New Baltimore is structurally unique. Chemically, it is anomalous, too, in combining typical group IliA Ga-Ge-lr ratios with significantly lower P- and Ni-values. Compare, for example, with Wabar and Norfolk. Previous suggestions by Merrill (1923d) and Stone (1932) that New Baltimore was a paired fall with Mount Joy and Pittsburg were already disproved by Henderson & Perry (1958: 368) ; their conclu­sion is fully supported here.

Specimens in the U.S. National Museum in Washington:

I ,470 g end piece (no. 710, 13 x 8 x 3 em) 748 g piece with artificial cleavage fracture (no. 710, 10 x 7 x

3 em) 167 g polished slice (no. 710,11 x 8 x 0.5 em) 600 g individual, loose kamacite grains (no. 710, ranging from 7 to

133 g) 50 g oxide-shales (no. 71 0)

New Leipzig, North Dakota, U.S.A.

46°22'N, 101 °57'W; 750 m

Coarse octahedrite, Og. Bandwidth 2.6±0.5 mm. Neumann bands. HV 205 ±10.

Group l,judging from the structure. About 6.7% Ni and 0.2% P.

HISTORY

A mass of 20.0 kg was found in 1936 by Daniel Buckwitz, Jr., on his farm on Route I, near New Leipzig, in Grant County. The corresponding coordinates are given above. Buckwitz notified a senator from North Dakota

Figure 1249. New Leipzig (U.S.N.M. no. 121 0). The main mass now weighs 17.0 kg after an end piece has been removed (right). Regmaglypts are prominent. Scale bar approximately 4 em. S.l. neg. 1631A.

who, in turn, established connections with the U.S. National Museum, and in 1937 the mass was purchased for $150. "It is deeply gratifying for me to hear that you found the specimen to be of such type that you could pay me this amount for it. I was confident that you would do the right thing and I assure you that I greatly appreciate your kind

New Baltimore - New Leipzig 897

consideration in the matter," wrote Buckwitz to the Secretary of the Smithsonian Institution on February 6th, 1937. The discoverer was "a man of poor circumstances, located in the worst drought area in the State of North Dakota" with an invalid wife, confined to her bed with arthritis. "The discovery of this meteorite on my farm and the sale of it is a blessing from Heaven for me and I thank God for it."

The meteorite has been briefly mentioned by A.D. Nininger (1937), but it is not described.

COLLECTIONS

Washington (17 .9 kg), Chicago (558 g), Calcutta (183 g), London (19 g), Tempe (19 g).

ANALYSES

No analysis has been performed. From an examination of the structure I would expect 6.7±0.2% Ni and 0.2±0.04% P with Ga-Ge-Ir concentrations characteristic for group I.

DESCRIPTION

The meteorite is a beautifully sculptured, angular mass with the overall cimensions of 30 x 15 x 12 em. On most of the surface it is covered by well developed regmaglypts, ranging from 1-3 em in diameter and 5-10 mm deep. Between the individual pits there are rounded knobs and ridges which serve to give the surface a very irregular outline. The knobs may attain dimensions of 7 x 2 x 2 em

Figure 1250. New Leipzig (U.S.N .M. no. 121 0). A coarse octahe­drite. Secondary grain growth has somewhat eliminated the previous Widmanstiitten pattern. Deep-etched. Scale bar 15 mm. S.I. neg. 1658.

or 3 x 2 x 2 em. A few deep pits indicate where troilite was removed by ablational melting; the largest has an aperture of 15 x 30 mm and is 20 mm deep. Near the middle of the oblong mass, a conspicuous, straight 6 em long crevice forms a 2 em deep and 3 mm wide and partly undercut scar; the incision was apparently formed by ablational

898 New Leipzig

melting of a troilite-schreibersite aggregate. One face, which may be termed the rear face during flight, is rather plane and covered with large shallow regmaglypts , typically 2.5-5 em across and 0.5 em deep. The oxidic fusion crust is

Figure 1251. New Leipzig (U.S.N.M. no. 1210). Rounded kamacite grain s with schreibersite at grain boundaries and Neumann bands in the interior. Scale bar 500 IL·

preserved as paper-thin coatings which, in places, cover 1-10 em 2 • It is rust colored from incipient corrosion , and in some places the weathering has proceeded to create 0.1-0.5 mm thick , terrestrial oxides.

A section through one of the knobs discloses the well-preserved heat-affected a 2 zone , ranging from 14.5 mm in thickness. A section through the massive part of the meteorite near one end showed a thickness of

\

Figure 1252. New Leipzig (U.S.N.M. no. 1210). The degenerated acicular plessite field was formerly situated in an a- a grain boundary, but due to grain growth it is now entirely within one grain. Etched. Scale bar 300 IL·

1-2 mm. It may safely be concluded that little of the mass has been lost by weathering, the highest reduction observed being of the order of 1 mm, and this only locally. The microhardness of the a 2 zone is 19 5± 1 0 . It decreases to a minimum of 160±10 at the transition from a 2 to a because

recovery has taken place here without visible alteration of the structure (hardness curve type II).

Etched sections dis~ay a coarse Widmanstiitten struc­ture of straight, short (w ~ 1 0) kamacite lamellae with a width of 2.6±0.5 mm. Late grain growth has eliminated many of the straight lamella boundaries and created more or less equiaxial grains, 3-15 mm across. Taenite and plessite may, therefore , be found inside uniformly oriented kamacite grains and, in addition, along grain boundaries. The kamacite has subboundaries decorated with 0.5 J.1

phosphides, and Neumann bands are well developed. The microhardness is 205±10, corresponding to a slightly work-hardened, unannealed kamacite matrix .

Taenite and plessite cover little more than 1% by area , mostly as dt:generated comb plessite fields , 1-2 mm across. Acicular plessite with 2-5 J.1 wide kamacite needles is also present. The taenite rims are tarnished due to carbon in solid solution.

Schreibersite is common as 2 x 0.3 mm skeleton crystals and lamellae and as 50-100 J.1 wide grain boundary precipitates. Rhabclites are ubiquitous, both as 5-20 J.1

prismatic rods and as a second generation of 1 J.1 crystals. Where the ablating surface happened to pass a larger schreibersite crystal this melted out in advance , and its cavity was immediately filled, at least partially, to a depth of 4 or 5 mm with metallic fusion crust.

Figure 1253. New Leipzig (U.S.N .M. no. 1210). Deformation has brecciated the schreibersite crystal and created numerous cracks along cubic cleavage planes of the kamacite . The fissures are now partially recemented by terrestrial lin10nite. Etched. Scale bar 200 !J..

No other minerals were positively identified in the sections, but troilite-daubreelite and graphite-cohenite are almost certainly present, judging from the exterior ablation grooves and from the general structure .

The meteorite displays several intercrystalline fissures, 10-100 J.1 wide . They are , of course, now partially filled with corrosion products, but it appears that at least some of

{ ' '

t. ll1 ~

,!;',/

I . • _ ·f';< ·,.· •. • ' . ._ ·< .,_

~~ .. \ 0:, • • J , L .............. ~· -~---r< -'"--"--> , , , . > '

0 h• '

' ' ,·· .., I

/

Figure 1254. New Leipzig (U.S.N.M. no. 1210). Heat-affected a 2 zone which has penetrated from above until it was stopped (temporarily) by the poor heat-conduction across a cracked grain boundary. Etched. Scale bar 300 J.L.

them were preatmospheric. For example, the regular smooth ingression of the a 2 zone is abruptly stopped at an open grain boundary at a depth of only 1.5 mm, while the zone in similar positions elsewhere is 3-4 mm thick. It seems that there was no heat conduction across this boundary when the meteorite entered the atmosphere, and the only explanation for this must be the fact that the grain boundary was already open. In other places grain bound­aries occur with severely brecciated schreibersite and troilite, the fragments of which are 5-50 J.1 across. They are recemented to a solid matrix by terrestrial limonite, but it appears that the material once loosely filled the fissures. The violent event that produced the fissure in the metal and fragmented the minerals, also displaced the two sides of the fissure slightly, as proved by the presence of bent Neumann bands near the fissure.

Preatmospheric, intercrystalline fissures in iron meteor­ites are much more common than generally realized. They probably originated at the time of the cosmic event that created the Neumann bands, and they have , therefore, normally existed for millions of years. The presence of preatmospheric fissures - both in the grain interior and along grain boundaries - makes it somewhat easier to understand why seemingly massive and very strong mater­ials, such as iron-nickel meteorites, frequently break up in the atmosphere and form showers. In calculations of reentry decelerations, it is unrealistic to insert experimental test values of massive iron-nickel material; the bulk strength of most iron meteorites is significantly lower than the ideal values because the meteorites contain numerous inclusions and, in addition, numerous cracks from previous shock events. The presence of microcracks in the metal and in the minerals also serves to explain the readiness with which a terrestrial corrosion attack penetrates to a depth of several centimeters in an apparently massive and otherwise well­preserved iron meteorite.

New Leipzig - New Mexico 899

New Leipzig is a coarse octahedrite structurally related to Campo Del Cielo, Gladstone and Seel:'isgen, and it will probably turn out to be a normal member of group I.

Specimens in the U.S. National Museum in Washington:

17.0 kg main mass with 12 x 5 em polished section at one end (no. 1210,26 xIS x 12 em)

341 g part slice (no. 1210, 12 x 6 xI em) 558 g slice (no. 121 0)

New Mexico, U.S.A.

An Indian ax of 130 g was found in a ruin in New Mexico and in !935 was recognized as of meteoritic origin (Nininger & Nininger 1950: 78). No particulars of the origin or discovery site are known.

The material which is in Tempe (No. 511.1 , 126 g), is an elongated ax-shaped mass, measuring 65 x 25 x 15 mm. At one end is a cutting

Figure 1255. New Mexico (Tempe no. 511.1). An Indian ax of 130 g. Apparently the owner acquired a single finger-shaped lamella of a coarsest octahedrite and, with minimum of work, shaped it to the appropriate form. Smoked with NH4 Cl. Scale bar 1 em. S.I. neg. 488A.

Figure 1256. New Mexico. Section through Figure 1255. The material is a single kamacitc crystal. Superficial working has bent the Neumann bands. Deep-etched. Scale bar 3 mm. S.I. neg. 488.

900 New Mexico -New Westville

edge, at the opposite end is a (recen tly) cut and polished surface. An examination of the structure discloses only a rather pure kama cite matrix, without Widmanstiitten structure and without any meteor­itic minera ls, such as taenite, schreibersite, troilite and cohenite. Slightly bent Neumann bands are, however, locally present along the surface. In a few places on the uncut surface there are signs of sligh t cold work with overfolded kamacite, but there are no indications that the ax should have been produced by forging or excessive cold work.

It appears that on some occasion the Indian had acquired a single finger-shaped lamella from one of the coarsest octahedrites of the American Southwest. Since such individual lamellae may from the beginning have shapes suggestive of an ax, the Indian needed only apply very little additional work, such as grinding, to finish his tool. As possible so urces, such irons as Navajo, El Burro and Sandia Mountains may be considered. The possibility that the material should be from some hexahedrite (Hey 1966: 340) appears, from st ructural considerations, much less likely.

New Westville , Ohio , U.S.A.

39°50'N , 84°47'W; 350m

fine octahedrite, Of. Bandwidth 0.42±0.06 mm. e-structure. HV 285 ±30.

Gro up IVA . 9.40% Ni, 0.47% Co, 0.14% P, 2.40ppm Ga, 0. 139 ppm Ge , 0.55 ppm Jr.

HISTORY

A mass of 4.8 kg was found in 1941 in a field near U.S. 40, about 3 km east of the Ohio-Indiana state line near New Westville, in Preble County. It was acquired by S.H. Perry and donated to the U.S. National Museum where it was thoroughly described with several photomicrographs by Henderson & Perry (1946).

COLLECTIONS

Washington (3,318 g), Madrid (343 g), Moscow (228 g), Chicago (206 g), Calcutta (203 g), Harvard (68 g).

DESCRIPTION

The overall dimensions of the oval mass were 16 x 10 x 6 em, and the recovered weight was 4 .8 kg. It is heavily corroded and continues to deteriorate under museum conditions of normal dry air conditioning. It is covered with 1-10 mm thick terrestrial oxides which easily spall off; and the Widmanstatten structure is clearly seen upon the surface because there is a preferential attack along the

octahedral planes. On sections it is seen how intercrystalline corrosion penetrates along the phosphide lined grain bound­aries and how the a-constituent of the plessite phase is particularly rapidly attacked. No fusion crust and no heat-affected a 2 zones are preserved. The mass has prob­ably lost a few centimeters of its original skin by corrosion.

Etched sections display a fine octahedrite structure of straight , long (~ ~ 40) kamacite lamellae with a width of 0.42±0.06 mm. The kamacite is hatched and of the variety which usually is ascribed to a shock transformation above 130 k bar, from a via E back to a-structure. The hardness is correspondingly high but somewhat irregular , 285±30. Plessite covers about 50% by area as comb and net plessite, as cellular "Gibeon" plessite, and as duplex a+ 'Y fields of varying fineness . A typical field will show a yellow taenite rim (HV 290±15) followed by a light-etching martensitic transition zone (HV 360±20). Farther inwards come dark­etching martensite (HV 350±20) and finally, for example, a duplex a+ "f mixture (HV 250±20). It is rather unusual that the duplex structure is softer than the adjacent kamacite lamellae , and the explanation is not obvious.

Schreibersite is common as 5-25 J.1 wide grain boundary veinlets. Occasionally they increase to I 00 or 200 J.1 in thickness, and they may then include a tiny , monocrystal­line, troilite nodule. Schreibersite is also common as 2-15 J.1

irregular blebs inside the plessite. The phosphide concentra-

Figure 1257. New Westville (Moscow). A fine octahedrite of group IV A. It is corroded , particularly along schreibersite-filled grain boundaries. Deep-etched. Scale bar 20 mm. S.l. neg. 36673.

NEW WESTVILLE - SELECTED CHEMICAL ANALYSES

percentage ppm References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Henderson & Perry 1946 9.41 0.61 0.10

Dyakonova 1958a 9.45 Jarosewich 1968,

pers. comm. 9.38 0.34 0.18 Schaudy et al. 1972 9.36 2.40 0.139 0.55

'~~

.... ~ -...;;

~ .. :v. ...

~

~

-

,•

Figure 1258. New Westville (U.S.N.M. no. 1412). Shock-hatched kamacite of high hardness (285 Vickers). Various plessite types. Fissured schreibersite at grain boundaries. Etched. Scale bar 400 p.. (Perry 1950: Volume 6.)

tion is in harmony with the analytically determined average of0.14% P.

Troilite blebs, 0.2-3 mm in diameter, occur with a frequency of about one per 15 cm2 . Only small ones were present in the polished sections, and they were all mono­crystalline. Several of the troilite nodules are developed around 0.1-0.5 mm angular, cubic chromite crystals, and the whole aggregates are surrounded by 20-50 JJ. thick, disc on tin uous schreibersite precipitates. Daubreelite was not observed.

New Westville is a weathered fine octahedrite related to Mart and Chinautla, but a little different in the details of the structure , indicating a slightly different story after the initial cooling period. Chemically, it is a typical group IV A iron.

Specimens in the U.S. National Museum in Washington:

2.63 kg half mass (no. 1412,10 x 10 x 6 em) 385 g cndpiece (no. 1412, 9 x 5.5 x 2 em) 200 g small sect ions and oxidi zed fragments (no. 1412)

N'Goureyma , Massina , Mali

Approximately 13° 51'N, 4 °23'W

Anomalous, polycrystalline, troilite-rich iron. Martensitic-plessitic matrix. HV 215 ±15.

Anomalous. 9.41 % Ni, 0.56 % Co, 0.05% P, 0.6% S, 0.07 ppm Ga , 0 .02 ppm Ge, 0.6 ppm lr.

The date of fall is questionable .

HISTORY

A mass of 37.7 kg was said to have fallen June 15, 1900 in Sudan near N'Goureyma, 20 miles north of

New Westville- N'Goureyma 901

Koakourou and Djenne. Unfortunately , no details of the fall have been published and even the locality is given differently by Meunier and Cohen. The mass was said to have been recovered from a one meter deep hole in clay, but it is not known how rapidly it was recovered . The mass was acquired by H. Minod (Comptoir Mineralogique et Geologique, Geneva), who cut and distributed it in 1900 and following years at a price of 2-3 Francs per gram. The meteorite was briefly described by Meunier (1901 ) , then much more detailed and with excellent photographs by Cohen (1901a) . A summary with all the essential observa­tions was printed in English (Cohen 1903d). Goldschmidt (1930) found 2 ppm platinum metals, and Goldschmidt & Peters (1932) found 5 ppm Pd and 1 ppm Au. Cobb (1967) found 0.2 ppm Au. El Goresy (1965) observed chal­copyrrhotite as an accessory mineral and gave a micrograph of the metallic fusion crust. Ramdohr (1967) gave a similar micrograph and discussed the fusion crusts on meteorites in general. Buchwald (1966) briefly discussed two micro­graphs that suggested an anomalously high cooling rate for N'Goureyma. Axon et al. (1968) , who presented similar photographs, proposed that such a structure might be the result of rapid reheating plus rapid cooling of an original monocrystalline meteorite with normal Widmanstatten pat­tern. Vilcsek & Wanke (1963) estimated the exposure age to be 215±20 million years . liimmerzahl & Zahringer (1966) found 280±190 million years, while Chang & Wanke (1969) found 200±20 million years. The amount of noble gases was determined by Hintenberger & Wanke (1964).

Figure 1259. N'Goureyma. The main mass before cutting, seen from two different sides . (Cohen, 190la.)

902 N'Goureyma

COLLECTIONS

Heidelberg (about 4 kg, blunt endpiece), Washington (I ,518 g), Chicago (990 g), Canbe_rra (97 5 g), Budapest (939 g), Hamburg (882 g), London (871 g), New York (85 2 g), Paris (711 g), Ti.ibingen ( 412 g), Vienna (346 g), Bally (312g), Calcutta (182g), Copenhagen (155 g), Oslo (144 g), Uppsala (137 g), Bonn (134 g), Yale (87 g), Prague (59 g), Moscow (58 g), Berlin (29 g), Strasbourg (26 g), Vatican (I 6 g). The end piece with the two holes, weighing 6,565 g, was offered for sale in 1921 and possibly passed into a private collection.

DESCRIPTION

The 37.7 kg mass was roughly wedge-shaped and 58 em long. Its largest width of 28 em occurred at one third its length. Varying between I and 9 em in thickness, the mass was so thin as to be bounded practically by only two surfaces which met along a pretty sharp edge. One surface, extending from the blunt leading edge, was more convex than the opposite that was flat or slightly concave. The meteorite was deeply grooved, with furrows that generally radiated from the blunt apex; and two holes, approximately

4 x 2 and 2 x I em in size, penetrated the thin shield near the trailing edge (Cohen 1901 a; 1903d). Cohen concluded from both the exterior, drop-like appearance and from the interior structure that the mass had remelted or at least softened throughout as it passed the atmosphere. Bedford (I 938) disagreed with this conclusion, and the present examination, likewise, shows that N'Goureyma only ablated in the way usually met within meteorites of oriented flight.

Figure 1260. N'Goureyma (University of Heidelberg). Close-up of the end piece showing prominent ridges and furrows radiating from a common apex. Scale bar approximately 3 em.

Figure 1261. N'Goureyma (U.S.N.M. no. 559). Almost full cross section of the thinner part of the mass. All troilite inclusions appear as more or less perfect spherules. The metal is a polycrystalline aggregate of inch-size precursor taenite grains. Deep-etched. Scale bar 2 em. S.l. neg. 1333.

N'GOUREYMA - SELECTED CHEMICAL ANALYSES

Cohen's analysis was performed on 8 g material which contained troilite and chromite (but not daubreelite, as reported in the original analysis); therefore, his S and Cr

percentage References Ni Co p c Cohen 190la 9.26 0.60 0.05 370 Lovering et al. 1957 0.56 Buchwald 1966,

unpubl. 9.50 0.55 0.05 Cobb 1967 9.62 0.51 Wai & Wasson 1970 9.26

values are very high. Berkey & Fisher (I 967) analyzed the meteorite for chlorine and found 1-8 ppm, which is high compared to that of other falls.

ppm s Cr Cu Zn Ga Ge Ir Pt

7700 1500 400 80 <2 <I

<2 34 <5

<60 0.067 0.0161 0.58

Figure 1262. N'Goureyma (Copenhagen no. 1904, 1588). Detail of the heat-affected zone. Fusion crust is out of focus at upper right. A troilite nodule is partially ablated away, but the pit is refilled with fusion crust from adjacent parts of the surface. Etched. Scale bar 100 1-' ·

Figure 1263. N'Goureyma (Copenhagen no. 1904, 1588). Several precursor taeni te grains showing grain boundary cracks due to low coherence across the troilite-rich boundaries. Also numerous troilite spherules in the grain interiors. Etched. Scale bar 2 mm.

The regmaglypts are 24 em in diameter on the convex side and somewhat larger and shallower on the flat side. The mass is covered with a black, matte, somewhat weathered oxidic fusion crust in which are numerous 0.1-1 mm pinpoint holes and elongated grooves from ablation-melted troilite. Already on the surface it may be readily seen that the tiny troilite bodies must be thread­shaped and uniformly oriented through the whole mass, parallel to its long direction. The ablation-melted metal has spilled over the edges and locally forms 1-2 mrn thick laminated deposits on the flat rear side. Otherwise it is 100-400 11 thick. It is a rapidly solidified dendritic-cellular aggregate of austenite with a significant proportion of interdendritic sulfide eutectics. The exterior parts of the fusion crust are rich in Fe-S-0 eutectics.

The fusion crust has a microhardness of 310±30. Under the fusion crust is a 2-3 mm thick, heat-affected zone which is difficult to observe optic3.lly but is characterized by its

N'Goureyma 903

microhardness of 180±20 as opposed to the interior hardness of 215±15.

The etched sections reveal three anomalous features: the polycrystallinity, the absence of Widmanstiitten struc­ture, and the fine distribution of troilite. The mass is a polycrystalline aggregate of original austenite grains, 24 em across. They appear to be elongated in the long direction of the mass, but unfortunately no good sections of this type were available since most of the meteorite originally was cut by Minod in parallel, 0.3-1 em thick slices perpendicular to its long direction. In the austenite grain boundaries are numerous wedge- and foil-shaped troilite bodies, typically 2 mm long and 0.1 mm thick. No superstructure, like dendrites or a washed-out Widmanstiitten structure could be found, so the assumption of any such preexisting structures must remain extrapolation without preserved evidence. The poly crystalline structure as seen today may, in fact, rather be the result of sintering at 1000-1 200° C, where sulfur-rich liquids promoted the densification. When the polycrystalline austenite cooled, the cooling rate must have been significantly higher than for Treysa, Bacubirito and other irons of corresponding composition that devel­oped a normal Widmanstiitten structure. In N'Goureyma not a single kamacite lamella is present ; the austenite is transformed to what looks like martensite at low magnifica­tion but at higher magnification is seen to be a duplex ex+ r structure that may well be termed a tempered martensite. The taenite forms oriented 0.5-1 11 wide, irregular ribbons that are situated in veined kamacite. The veins divide the kamacite into 2-5 11 wide cells. Neumann bands are absent. While the cooling rate was sufficiently rapid to prevent Widmanstiitten formation it did not completely suppress heterogeneous nucleation and growth around the troilite inclusions, where in several places a 10-150 11 wide zone of swathing kamacite may be found.

The matrix is best explained under the assumption that the austenite, under relatively rapid cooling, transformed to

Figure 1264A. N'Goureyma (Copenhagen no. 1904, 1588). The troilite forms sheets along the grain boundaries, but spherules in the grain interiors. Narrow, asymmetric rims of swathing kamacite are also visible. Etched. Scale bar 300 1-' ·

904 N'Goureyma

a2 and that this metastable phase - either immediately or later under reheating - decomposed to fine-grained, pless­itic a+ 'Y. The experimental background for this interpreta­tion has been given by Buchwald (1966).

The omnipresent troilite inclusions of the grain interior are, in sections, perpendicular to the long dimension of the meteorite, circular or crescent-shaped. On sections parallel to the long direction of the meteorite a major part of the troilite inclusions have the form of commas and droplets, always tapering against the same thin end of the mass. This "fluidal" structure is rare in iron meteorites but may be related to the uniformly oriented but larger troilite "belem­nites" of Cape York, Chihuahua City, Santa Luzia, Santa Rosa and Bendego.

The troilite contains numerous, euhedral chromite crystals that range from 10 J.1 to 1 mm in size and are somewhat brecciated. Daubreelite is absent. A few grains,

Figure 12648. N'Goureyma (Copenhagen no. 1904, 1588). The troilite nodules have been exposed to deformation. They are decomposed into cells with undulatory extinction, separated by recrystallized and sometimes shock-melted material. Polished. Crossed polars. Scale bar I 00 J.!..

Figure 1265. N'Goureyma (Copenhagen no. 1904, 1588). The duplex matrix at high magnification. Cell boundaries in kamac­ite (K). Irregular ribbons and lamellae of taenite. Etched. Scale bar 30J.L.

5-10 11 across, of chalcopyrrhotite are located at the edge of some troilite grains, closely associated with fine-grained dispersed iron. The troilite is subdivided by shear zones in 50-100 J.1 passive blocks that display undulatory extinction due to plastic deformation. The shear zones themselves and the interphase boundaries against the metal are recrystal­lized to 1-5 J.1 grains and may even be melted locally. The structures are probably due to shock.

In the metallic matrix, thin oriented troilite platelets are common. They are typically 200 11long but only 1-2 J.1

thick and polycrystalline. They may represent high temper­ature cracks which became filled with troilite precipitates before the cracks could be sealed by diffusion.

Point counting of the macroscopically visible sulfides on a 9.5 cm2 section gave :

4 troilite inclusions ;;. I mm in diameter, totaling 3.5 mm2

75 troilite inclusions 0.3-0.9 mm in diameter, totaling 15.0 mm2

90 troilite inclusions <: 0.2 mm in diameter, totaling 1.0 mm2

The total of 19.5 mm 2 corresponds to about 2 volume % FeS or 0.45 weight % S. Cohen's analytical result of 0.77% S was evidently from a section still richer in troilite.

Schreibersite and rhabdite were not observed, in agreement with the low analytical value of 0.05% P. Cohen (1901a: 155) reported a 30 x 2 mm plate-shaped schreibers­ite crystal near the fusion crust. This must, however, be a misinterpretation of some of the near-surface cracks that are partially filled with fusion crust. Since the cracks display veinlets of fused metal, they must, at the latest, have formed in the atmosphere - probably by simultaneous fissuring during the violent deceleration and ablation melting of the low-melting grain boundary troilite.

The meteorite is more corroded than other observed falls. The crust is partially converted to limonite, and the troilite nodules are somewhat weathered. Limonitic vein­lets, 1011 wide, are common near the surface, and the large, intergranular cracks that locally attain a width of 1 mm and threaten to split whole sections are also corroded. The chlorine content, as reported by Berkey & Fisher (1967),

Figure 1266. N'Goureyma (Copenhagen no. 1904, 1588). In the duplex matrix there are several lamellae similar to this one. It is apparently a troilite lamella, less than 1 J.l. thick, which entirely disrupts the continuity of the a+ 'Y matrix. Etched. Scale.bar 30 J.!..

Figure 1267. N'Goureyma (Copenhagen no. 1904, 1588). A cubic chromite crystal (chipped) with two troilite blebs (T). Etched. Scale bar 300 J.l..

Figure 1268. N'Goureyma (Copenhagen no. 1904, 1588). Troil· ite (T) and a large, sheared chromite crystal (below). A cluster of small idiomorphic chromite crystals is situated in the troilite at the top. Etched. Scale bar 50 J.l..

suggests some terrestrialization, too. It appears that the mass was left exposed to the tropical climate for a considerable period after its fall, and it is, in fact, doubtful whether the reported fall date can be relied upon.

N'Goureyma is an anomalous meteorite, structurally as well as chemically. It is, so far , the meteorite with the lowest concentration of gallium and germanium. It has been termed a brecciated or a recrystallized octahedrite, but these descriptions are misleading since no true Widmanstiit­ten pattern is present; and the "breccia" comes from a misinterpretation of a ustenite grain boundaries. / N'Goureyma may be the result of aggregation plus sintering of fine-grained material, followed by a cooling that was rapid relatively to what the normal octahedrites underwent. The metallic part of N'Goureyma resembles in numerous respects the metal of Tucson (Ring).

Specimens in the U.S. National Museum in Washington:

895 g slice (no. 559, 25 x 6 x 0.7 em) 95 g part slice (no. 1499, 8 x 5 x 0.5 em)

N'Goureyma- Niagara 905

148 g slice (no. 2963, 16 x 6 x 0.3 em) 380 g slice (no. 2964, 17 x 8 x 0.5 em)

Niagara, North Dakota, U.S.A.

Approximately 48°0'N, 97°56'W

Coarse octahedrite, Og. Bandwidth 1.4±0.2 mm. Neumann bands. HV 220±10.

Judging from the structure, a group I iron related to Toluca, with about 8% Ni, 0.5% Co and 0.2% P. Perhaps a mislabeled Toluca specimen.

HISTORY

According to Preston (1902a), a small mass of II5 g was found two miles southeast of Niagara, Grand Forks County, in the early part of August, I879. It was discovered by F. Talbot who was making a collection of rocks and minerals on his father's ranch. The meteorite was acquired by Ward's Natural Science Establishment and distributed in small fragments around I902-04 (see, e.g., Price List of I904 and Ward's catalog I904a: I9). Farring­ton (19I5: 342) reviewed the literature.

COLLECTIONS

Chicago (25 g), Yale (I9 g), London (I6 g), Vatican (8 g), Berlin (3 g).

ANALYSES

Preston (1902a) reported 7.37% Ni, O.I3% Co , 92.67% Fe; but this analysis appears inadequate.

DESCRIPTION

The following paragraph is quoted from Preston (1902a) since he is the only one who has seen the entire sample:

"The meteorite measured 30 x 40 x 50 mm and weighed 115 g. lt was very much oxidised, of a brownish-black color, and showed no trace of the original crust whatever. In sawing it crumbled into small fragments of from 2 to 4 or 5 grams weight each. The largest piece obtained weighed 26 g. On etching two pieces composed of unoxidized iron, an octahedral structure was strongly brought out in the Widmanstiitten figures, the kamacite plates being somewhat broad, with a second series of markings of hairlike lines upon them about the size of the Neumann lines on the Braunau iron,"

The largest piece mentioned above came to the Field Museum, Chicago, and has kindly been loaned to me by Dr. E. Olsen. The sample measures 2I x 2I x II mm and contains some of the original oxidized surface. The etched section displays a coarse Widmanstiitten structure of straight, short (~ ~ IO) kamacite lamellae with a width of I.40±0.20 mm. The kamacite is rich in subboundaries decorated with I J1 rhabdites. It also shows numerous Neumann bands, some of which are visibly bent. The microhardness is 220±IO, in accordance with the distorted, cold-worked structure.

906 Niagara -N'Kandhla

Taenite and plessite cover I 0-15% by area, both as comb and net plessite and as spheroidized and martensitic varieties. The '}'-spherules of the sphero-plessite are 2-20 J1

across, while the '}'-lamellae of the pearlitic plessite are 0.5-2 J1 wide. Selective corrosion has converted the duplex textures to beautiful patterns of 'Yin black "limonite." The martensitic varieties of the fields exhibit acicular high­nickel, high-<:arbon zones, intercalated with retained austenite. In places, the plessite shows numerous pointed a-platelets only 1-5 J1 wide.

Schreibersite occurs as a 2 x 3 mm single crystal and as numerous 10-80 J1 wide grain boundary precipitates. The rhabdites are 1-10 J1 across. Due to plastic deformation of the metallic matrix, the brittle phosphides are sheared ; the rhabdites are, e.g., often shear-displaced their own width. The bulk phosphorus content is estimated to be 0 .20±0.05%.

Cohenite occurs as an irregular 0 .2-0.5 mm wide rim around the large schreibersite crystal. It is fissured, and the fissures are filled with terrestrial corrosion products . De­composition to ferrite plus graphite has not begun. The schreibersite-cohenite aggregate is enveloped by a I rom wide rim of swathing kamacite .

Only a single troilite inclusion was noted on the small section. It was a 25 J1 wide single crystal with some pentlandite veining from terrestrial corrosion.

The fragment is oxidized and penetrated by 0 .1 mm wide limonite veins. No heat-affected a 2 zone could be detected. The original surface can , however, not have been far away , since a small amount of fusion crust was identified. It filled a 0.1 rom wide crack which extended from the surface to a depth of I mm. It was metallic and formed an extremely fine, dendritic ( ~ I p) melt, suggest­ing rapid solidification by heat conduction through the cold walls of the fissure.

Niagara seems to have been a fully developed sample of 115 g except for some loss by terrestrial corrosion. It is a typical coarse octahedrite closely related to Toluca and the other group I irons. In -its detailed morphology and struc­ture it is, in fact, indistinguishable from the numerous small specimens collected in the Toluca strewnfield, compare page 1209. Whether it is , in fact, a mislabeled Toluca specimen is impossible to say at this late date . Another, more remote, possibility is that Niagara is a minor fragment of New Leipzig; the distance between the localities is, however, 400 km and the structures are different in several details.

Nico. See Gibeon

Nieder Finow, Frankfurt (Oder), East Germany

52°50'N, l3° 56'E

A small mass of 287 g was found in 1940 near Nieder Fin ow, Kreis Eberswalde, in Brandenburg. It was described as a coarse octahedrite by Nebern & Schuller (1950); the entire mass is in the Humboldt University, Berlin (Wappler & Hoppe 1969: 375). A preliminary analysis by Wasson (1972: personal communication) shows 8.27% Ni, 76 ppm Ga, 271 ppm Ge, 2.6 ppm Jr. This, together with the structure, suggests that Nieder Fin ow is a group I iron related to Bischtiibe and Toluca.

Niro. See Verkhne Udinsk

N'Kandhla, Natal, South Africa

28° 46'S, 30°38'E

Medium octahedrite, Om. Bandwidth 0 .85±0.12 mm. Decorated Neumann bands. HV 250±15.

Group liD. 9.96% Ni, 0.64% Co, about 0.3% P, 71 ppm Ga, 83 ppm Ge, 18.5 ppm Jr.

HISTORY

A mass of about 17.5 kg was observed to fall on August I , 1912 at approximately I :30"p.m. in the district of N'Kandhla near the junction of the Buffalo and Tugela Rivers. Stanley (1914), who described the meteorite and gave numerous photographs, also published the reports of five eyewitnesses; from these the following information has been extracted. Dedica, the wife of a Zulu chief, was cutting grass near her kraal when she heard a loud explosion. Then all the hillside was filled with a deafening

• Figure 1269. N'Kandhla (U.S.N.M. no. 2611). Violently folded kamacite and taenite at the surface. The heat-affected 0< 2 zone extends from the surface to A. The deformation is either preatmos­pheric or due to severe disruptive forces during atmospheric flight. Etched. Scale bar 500 J.L.

N'KANDHLA - SELECTED CHEMICAL ANALYSES

percentage ppm References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Cobb 1967 0.64 272 60 19 Wasson 1969 9.96 71.8 83.3 18

sound which grew louder until she heard and saw the meteorite strike the ground five meters away. Stones flew in all directions, and she threw herself on her face in a great fright; later, she never dared look at the meteorite, nor go to the spot. The native catechist reported that the mass fell almost vertically and made a 25 em deep and 60 em wide hole in the sparse soil that covered the vertical schists. The meteorite crushed a boulder, rebounded and rolled about five meters downhill. The grass where it came to rest was undamaged, so the mass could not have been very warm. The sergeant of police had heard a huge explosion and feared a disaster at one of the Natal coal mines. The direction of the traveling meteorite was uncertain, but it appears to have come from west or northwest ; the smoke trail was shifted by the prevailing winds to a spiraling column before it disappeared after a few minutes.

COLLECTIONS

London (17 .1 kg main mass and 196 g pieces), Wash­ington (146 g), Copenhagen (30 g).

DESCRIYfiON

The flattened angular mass has the approximate aver­age dimensions of 20 x 18 x 12 em. It is irregularly covered with regmaglypts, 2-3 em in diameter. It has several cracks; the largest runs at least 16 em along the surface, is 1-2 mm wide and extends to an unknown depth. Fusion crusts of melted metal and melted oxides cover the whole surface and also penetrate several millimeters into some of the fissures, proving that these formed before the meteorite impacted the ground. In one place an open crack had been partially filled with laminated deposits, 200 J.1 thick; when subsequent ablation cut across the fissure, it was covered with numerous layers of fused metal and fused oxides that eventually built up to a 300 J.1 thick, sealing cap. The metallic deposits have solidified in dendritic-cellular pat­terns with 1-2J.l spacings of the dendrites. The microhard­ness is 450±30. In the metal there are many 2-30 J.1

dendritic oxide spherules. The oxidic deposits are not so obviously laminated ; they contain scattered metallic spher­ules ranging from 2-30 J.1 in size. The dark wiistite phase is primarily preserved near the metallic matrix and near the metallic inclusions, while the lighter magnetite phase is developed along the wiistite grain boundaries and as a continuous, 100-200 J.1 thick, exterior layer.

Under the composite fusion crusts is a 2-2.5 mm thick heat-affected o:2 zone with a microhardness of 215±1 0 . The rhabdites and other phosphides are melted in the outer 50% of the zone and thin ( ~ 1 J.l.) stringers of phosphide melts connect several of the phosphides and the taenite.

The interior displays a medium Widmanstatten struc­ture of straight, long (W ~ 25) kamacite lamellae with a width of 0.85±0.12 mm. The kamacite has subboundaries, decorated with 1-2 J.1 rhabdites and a profusion of densely spaced Neumann bands. At high magnification the Neu­mann bands and numerous slipplanes are seen to be heavily decorated by 0.5 J.1 rhabdites and submicroscopic particles

N'Kandhla 907

(< 0.3 J.l) of what may be carbides. The microhardness of the kamacite is 250±15.

Taenite and plessite cover about 30% by area. The taenite has brown-etching borders which stand in marked contrast to the martensitic-plessitic interiors. A complete plessite field will have a 10-20 J.1 stained taenite border, followed by taenite with a few, sharp martensite needles. Then follows a zone of dense martensite and then a tempered martensite. The interior is an, optically, easily resolvable duplex a+ 'Y mixture, the directions of which clearly reflect the martensite orientation and the bulk Widmanstatten structure, but on a very reduced scale. The stained taenite borders have a microhardness of 360±25; in the heat-affected zone they are annealed and are as soft as 165±15.

Schreibersite is present as 0.2-0.4 mm wide, angular bodies centrally in some of the kamacite lamellae. They are monocrystalline but brecciated. They are often associated

~~y·;~?;~\;;c£fJ41~ /~/)~~~$;! u·· ... · ·· · ··• · · ·•· ··· ~ "''7.!' 411A" , ·· ~$~~~~;:.. . /, fl!~'!!:l!i ;;-:•, ~- ;e..,:r.r. -;,~· · ·,:-, . . ,.,_, " · :/!;4!:-, / ·S:tl r 'A-l.:-r~~- tJ..:1: ~.~.:~ff·_,-· .·. ; ,. ·~~~ · f._', : .. J:./"1- r:_~~t..: ,.._·':,.~';~/."J5- i,ft/."f. 1' l ·;' ' • '.· . !J'-:.,. 'fo. : F "·f'¥!J1F·· kiA~:~ · tt(.t·.,. ::~!j -/·,' J.::; ·:- l . ·'{f:A -~- ... . ;;;; •. . I ( '{•, - .r

1:(-r.-r;,,...l, ;.' · ,., ;:jji·~ ••!',:"; ·•. . · !II • '·1~:·· I "(f} ' .·, ' . • . • , f·id •:f·" •t·r:.~:/··:,· .>,·,:; ... :- ._J/·! 1; : •,;~o.i( . . .• l:~~ ;: ~ ;,{ .. _:_;.·_"' ~~·;,<r!/d'·· :· .~.. ;..;.:;j<,i::: ;,\~.:~1J.t . ·:.:~ ./"

- ... : ~ .. . ' ~ · • ., . n::, .. ).~ ;~lv ~-.. -/fi:..~ ~- :' .·:·Vnt· · ~ · ··: · · • # ./H··, .. 1 ... <.·/:.'Ji!c,.j!f-'t"::-·:;. ~!f#.'' t' ;•. 1\ · · . . • . · ~ • ••. ,, './..f.",'f., .,. ~·"'"·-~'~'- ~~

~'~J~~ ·: '/(· ;) · · ... . · :· · . / 1 1r ,'l'i ~!}A'f',·':' '!i-k,.~/-.f.c ,'f?~ M.'V.' J 1/. r'• • . I '· / . .; •Jf/.•'.Y.l ~ .,-, • .,.~ "ti:ril /, '.'/ '; I ' }>• ~(~d >! .": )1':./""- • •",~ . ,_ .:'}!iii

~J; ;. :. 1,· : ,.......____, ~ ,. ; , ' .l r • j _., ... ·~~ _,.~-~

Figure 1270. N'Kandhla (U.S.N.M. no. 2611). Fusion crust (above). The level of kamacite (K) is higher than that of taenite (f) and schreibersite (S) due to the higher melting interval of kamacite. The heat-affected a 2 zone is anomalous because the kamacite is very rich in fine precipitates. Etched. Scale bar 50 1-l·

r.4!.·1L~~ ... r

1 Figure 1271. N'Kandhla (U.S.N.M. no. 2611). Typical development in N'Kandhla. The kamacite appears gray and striated due to a large number of fine particles; see Figure 1272. Etched. Scale bar 500 1-l·

908 N'Kandhla - Nocoleche

Figure 1172. N'Kandhla (U.S.N.M. no. 2611). Detail of the heat­affected 012 zone. The kama cite has been through an 01-> 'Y-> 01 2

transformation, but slipplanes and Neumann bands are still visible due to their heavy decoration with minute 'Y- and phosphide particles. Etched. Scale bar 40 p..

with a little troilite and daubreelite that apparently have acted as nucleating bodies for the phosphides. Schreibersite is further common as 20-40 J.l wide grain boundary precipi­tates and as irregular 5-25 J.l blebs inside the coarser plessite fields . Rhabdites are present as 1-2 J.l prisms in some kamacite lamellae. The bulk phosphorus content is esti­mated to be 0.25-0.30%.

Although no graphite or cohenite was observed, there are structural indications of carbon being present. The numerous submicroscopic particles that decorate the slip­planes of kamacite and taenite (in the 500-700° C zone), the slight carburizing of the surface immediately under the metallic fusion crust, the hardness of taenite, the staining behavior of taenite and the morphology of martensite are such indications. A bulk carbon content of 0.03% as found by Stanley (1914) may be sufficient to influence the structure in the indicated way.

Troilite occurs with daubreelite as 0.2-0.5 mm blebs that are usually more or less embedded in schreibersite . The troilite is shock-melted and has injected 1-2 J.l wide veinlets into the brecciated schreibersite. The daubreelite is partially dissolved and may be found as 5-10 J.l subangular fragments dispersed through the troilite, which has a grain size of 1-5 J.l.

On some near-surface specimens the kamacite lamellae are distorted. The corresponding surface is severely de­formed, either from impact against the boulder or from artificial hammering.

N'Kandhla is a medium octahedrite with a close structural relationship to Carbo, Elbogen and Puquios. As shown by Wasson (1969) these - with a few other meteorites - form the chemical group liD.

Specimens in the U.S. National Museum in Washington:

10 g part slice (no. 2397, 2 x 1 x 0. 7 em) 128 g part slice (no. 2611, 7.5 x 4 x 0.9 em)

Nochtuisk, Yakutsk Autonomous SSR 59°59'N, 117°35'E

Only four fragments, weighing 4 , 2, 1 an·d I gram, respectively, were found in the gold washings near Nochtuisk in 1876. Of these, a 3¥.. g specimen is in the British Museum and 1 gin Berlin. They appear to be fragments of a coarse octahedrite. For references, see Hey (1966: 344).

Nocoleche, New South Wales, Australia

29°52'S, 144°13'E

Anomalous mixture of granulated and Widmanstiitten textures. Decorated Neumann bands. HV 177±8.

Anomalous. 6.42% Ni, 0.47% Co, about 0.17% P, 49 ppm Ga, 148 ppm Ge, 8.2 ppm Ir.

HISTORY

A mass of 20.0 kg was reported in1895 by George Raffel. It was lying upon the surface of stony ground at a spot five miles southwest of Nocoleche Station, near Wanaaring, in Ularara County. The coordinates are given differently by various authors; those above are from Hey (I 966: 344). The meteorite was acquired by the Australian Museum, in Sydney, where it was described with photo­graphs of the exterior and of etched slices by Cooksey (I 897). Ward cut a few large slices from the mass and figured one of them (Ward 1904a: plate 3), presently in Chicago. Hodge-Smith (1939: 16 and plate 7) gave other views of the meteorite. Schultz & Hintenberger (1967) determined the amount of occluded noble gases, while Voshage (1967) by the 4<X.j41K method estimated a cosmic ray exposure age of 250±70 million years.

COLLECTIONS

Sydney (13.0 kg), New York (2.0 kg), Chicago (1.12 kg), London (950 g), Washington (203 g), Vienna (169 g), Harvard (141 g) , Copenhagen (100 g), Perth (57 g), Vatican (46 g), Bonn (45 g), Ottawa (23 g), Calcutta (22 g), Stockholm (17 g), Berlin (12 g).

DESCRIPTION

The mass has the maximum dimensions of 31 x 28 x 13 em, but because of its rugged shape with many reentrant parts, the weight is as low as 20 kg. At one end is a projecting knob , connected to the main mass by a slender neck, almost in the same style as seen on the Thule meteorite . At least two of the large, parallel slabs cut by Ward pass through a huge, hemispherical cavity, about I 0 em in diameter and 6 em deep. Similar pits are present on, e.g., Sacramento Mountains , Gibeon, Filomena and Maria Elena, and they appear to be preterrestrial and not due to corrosion. Some corrosion has, however, occurred. In places Nocoleche is covered by 0.5-3 mm thick crusts of terrestrial oxides; and, on the sections examined, the heat-affected a2 zone has been removed. On the average more than 2 mm is lost due to corrosion. The Neumann bands are selectively corroded because they are sensitized by fine phosphide precipitates.

Etched sections present an anomalous structure which contains elements of New Baltimore, Arispe , Santa Rosa and Dungannon but, on the whole, is unique. About 70% by area is covered by a medium-coarse Widmanstatten

Figure 1274. Nocoleche (U.S.N.M. no . 1557). Two kamacite grains with prominent Neumann bands and sheared rhabdites. Etched. Scale bar 100 J.L.

Nocoleche 909

structure, but this is in irregular patches broken by lobed kamacite grains. The uniform orientation of the Widman­stiitten lamellae proves, however, that Nocoleche once was a single austenite crystal.

The Widmanstiitten lamellae are straight and long (~ ~ 20) and range in width from 0.8 to 2.0 mm. The irregularity is mainly due to their lack of confinement by taenite and plessite. Plessite proper was only noted once, as a 0.5 x 0.5 mm field , on 20 cm2 ; and taenite is also only present in small amounts, as 10-75 J1 wide bands that often

Figure 1275. Nocoleche (U.S.N.M. no. 1557). A narrow schreibers­ite crystal along a kamacite grain boundary. A carbide was formerly asymme trically precipitated upon the schreibersite, but cosmic annealing decomposed it to granulated ferrite and lamellar graphite (black). Etched. Scale bar 100 J.L.

Figure 1276. Nocoleche (U.S.N.M. no. 1557). Daubreelite (D) and troilite (T). The troilite is shock-melted and rapidly solidified. It displays characteristically curved cell walls. Polished. Scale bar 300 J.L.

NOCOLECHE - SELECTED CHEMICAL ANALYSES

References

Lovering et a!. 1957 Wasson 1969

percentage Ni Co P

6.42 6.4

0.47

c s

Reed (1969) found the kamacite to have 6.4% Ni and 0.10% Pin solid solution.

Cr

101

Cu

124

ppm Zn Ga

43 49.3

Ge

134 148

Ir Pt

8.2

910 Nocoleche- Nordheim

show a martensitic-acicular interior. Its hardness is, how­ever, low (200± 1 0), corresponding to well-annealed taenite. The low amount of r-phase may be expected at the 6.4% nickel level.

The irregular kamacite grains are more or less equiaxial and range from 1.0-25 mm in size. A considerable propor­tion of them, and perhaps all, appear to be developed as a form of swathing kamacite around large and small inclu­sions of troilite . The areas with Widmanstiitten pattern are, on the other hand, practically free of foreign inclusion. It appears, therefore, that the irregular mixture of Widman­stiitten and granular structure is due to nucleation effects, the troilites having formed kamacite grains around them­selves some time before the nuclei-free remainder trans­formed homogeneously to an octahedral pattern. New Baltimore is a parallel example.

The kamacite has numerous subboundaries and Neu­mann bands. Both types are richly decorated with phos­phides, generally smaller than 1 J1 in size. The kamacite has a hardness of 177±8.

Schreibersite occurs as 10-50 J1 wide grain boundary precipitates and as similar sized blebs inside plessite and in places where plessite was previously present. Rhabdites are ubiquitous as 1-10 J1 tetragonal prisms. The bulk phos· phorus content is estimated to be 0.15-0.20%.

Troilite is common as nodules, 5-16 mm in diameter, and as smaller blebs 0.5-2 mm across. The troilite contains 10-20% daubreelite in the form of parallel, 1-400 J1 wide bars. Also , a few euhedral chromite crystals (HV 1125±50), 0.5-1 mm in size, are present locally, frequently in contact with the daubreelite. The troilite is shock-melted and has dissolved a significant part of its kamacite walling. It has solidified to 1-3 J1 fine-grained iron-sulfur eutectics. The associated minerals, daubreelite, chromite and a little schreibersite, are brecciated and partly dispersed as 1-25 J1

fragments in the troilite. The troilite has been injected several millimeters out into the adjacent metal grain boundaries which have been opened. Since the fissures, 10-100 J1 wide, became only partially filled, they were an easy prey to corrosive attack when the meteorite landed.

Previously cohenite must have been common inside some of the plessite fields. The fields may be identified as 1-5 mm wide rhomboidal and triangular patches which now form a confusing network of recrystallized, serrated a-grains, taenite spherules and ribbons, and schreibersite blebs, the whole crisscrossed by feathery graphite veins. The morphology resembles, on a reduced scale, the decom­position products of cohenite in, e.g., Wichita County, and also somewhat resembles the decomposed plessite carbide roses of Kokstad and Santa Rosa. The graphite forms 100400 J1 long and 5-20 J1 wide plumose structures, per­haps with a crack along their midrib; and the associated recrystallized a-phase is very soft, HV 116±3, indicating a very low amount of nickel. It appears that the structures are best understood as original plessite-cohenite roses which at a late annealing decomposed to low-nickel kamacite

( ~ 2% Ni) and graphite in situ and incorporated the rather passive taenite and schreibersite blebs which already were present in the cohenite.

In the kamacite, and sometimes inside 10-25 J1 wide schreibersite bodies, there are numerous hard, rose colored precipitates of carlsbergite. They occur as oriented plate­lets, typically 40 x 1 J1 in size in the kamacite and as irregular blebs in the grain boundaries.

Nocoleche has an anomalous primary structure, having formed both granular and Widmanstiitten textures on cooling; the granular areas appear to have formed first by heterogeneous nucleation and growth around inclusions, while the Widmanstiitten structure formed later in the inclusion-poor parts by homogeneous nucleation. The secondary structures, as the shock-melted troilite, the decorated Neumann bands and the decomposed cohenite, appear to be due to shock and its associated relaxation heat. Nocoleche resembles New Baltimore and Mount Dooling a little, but they are all somewhat different in their trace-element concentrations and are best treated as anom­alous individuals, falling outside the groups.

Specimens in the U.S. National Museum in Washington:

l 77 g part slice (no. 1557, 6 x 3 x 1.2 em) 26 g part slice (no. 2967, 4 x 2.5 x 0.4 em)

Nordheim, Texas, U.S.A.

28°53'N, 97°34'30"W; 100m

Ataxite. HV 240±20.

Anomalous. 11.67% Ni, 0.51% Co, 0.04% P, 0.55 ppm Ga, 0.64 ppm Ge, ll ppm Ir.

HISTORY

A mass of 34 pounds (I 5.4 kg) was found in August 1932 by Hugo Schlosser on his farm 5 km south of Nordheim, De Witt County . The cotton field in which it was discovered had been cultivated for the first time during

Figure 1277. Nordheim (Los Angeles). An ataxite displaying oriented diffuse streaks. Four minute kamacite spindles are also seen. Etched. Scale bar 400 /-1.

the 1932 season, so the meteorite was probably turned up by the plow earlier that year. The mass was heavily weathered and covered with loosely attached magnetic scale, 2-4 millimeters thick, most of which came off in the course of handling . The remaining mass weighed 15.11 kg. It was acquired by the Texas Memorial Museum in Austin and was later fuHy described by Barnes (1939b) who presented an analysis and 11 photographs. Perry (1944: plate 20) gave two photomicrographs typical of the struc­ture. The coordinates as revised with the aid of a 1:24 ,000 map are given above.

COLLECTIONS

University of Texas, Austin (main mass), Washington (1 ,094 g).

DESCRIPTION

According to Barnes, the meteorite was of irregular angular shape with the extreme dimensions of 21 x 19 x 13 em. He found no fusion crust or regmaglypts, evidently because the corrosion had removed these features. The polished slice in the U.S. National Museum has no heat-affected rim zone but, on the contrary, shows how corrosion progresses inwards in the way typical for old ataxites. The fine-grained kamacite is selectively converted to limonite to a depth of 0.5-5 mm, while the taenite survives temporarily and serves to anchor the corrosion products. Often the attack is rhythmically developed in shallow bowls, from 1-15 mm across and from 1-5 mm deep. Similar features are seen in, e.g ., Cape of Good Hope,

Nordheim 911

Hoba and Kokomo. Corrosion further attacks along a few 0.1 mm. wide cracks that extend up to four centimeters inwards. It is interesting to note how well the sulfides are preserved. A 200 11 troilite-daubreelite nodule embedded in the limonitized crust was not attacked at all, for example. Contrary to common opinion, the sulfides, particularly if monocrystalline, may survive the a-iron phase for a long time and may even decompose after the -y-phase occasionally.

Polished and etched sections display an ataxitic struc­ture, marked only by oriented streaks and by scattered troilite inclusions. The diffuse streaks are uniformly ori­ented across the section; at least seven different directions are visible, suggesting that they are unrelated to the normal Widmanstiitten transformation which would, at most, account for four directions on an arbitrary section. Upon microscopic examination the streaks are seen to be a little richer in a-phase than the surrounding matrix. The taenite blebs and ribbons in the streak zones are less oriented than in the surroundings, but the streaks remain enigmatic.

The matrix is a fine-grained intergrowth of kamacite and taenite produced from an homogeneous taenite matrix. The intergrowths are oriented in a Widmanstiitten pattern uniformly developed across the whole section, indicating that the parent material was a single taenite crystal. The kamacite is veined and thereby subdivided into 3-5 11 cells, while the taenite is in the shape of 1-2 11 wide, irregular

· ribbons . Islands, 5-10 11 across, are developed as micro­plessite with an outer 1-2 11 taenite rim and a duplex

Figure 1279. Nordheim (Los Angeles) . Duplex matrix with diffuse streaks. The two white streaks are richer in kamacite than the

Figure 1278. Nordheim (Los Angeles). A cluster of kamacite adjacent dark matrix and contain better homogenized and spheroid-spindles in a rather dense"'+ 'Y matrix. Etched. Scale bar 50 p.. ized taenite particles. Etched . Scale bar 50 p..

NORDHEIM - SELECTED CHEMICAL ANALYSES

Gonyer also reported 0 .02% chlorine, which was interpreted as lawrencite, although the mineral was not actually seen. Considering the weathered state of the

percentage References Ni Co p I c Gonyer in Barnes

1939 11.69 0.51 0.04 Schaudy et al. 1972 11 .64

meteorite, it is more likely that the chlorine is mainly of terrestrial origin, accumulated during a long exposure to ground water.

s Cr Cu ppm Zn Ga

0.55

Ge Ir Pt

0.64 11

912 Nordheim - Norfolk

interior, difficult to resolve optically. The microhardness of the matrix, averaging over numerous a+ r units, is 240±20.

Alpha needles occur scattered through the matrix with a frequency of 0.8 per mm2 • They are usually 10-30 J.1 wide and about 10 times as long. When they are best, they are seen to be oriented parallel to the Widmanstiitten directions of the matrix. Some of them have been nucleated by 2-10 J.1

daubreelite and troilite blebs which are now engulfed by the lamellae, but the majority are inclusion free.

Schreibersite and rhabdite are absent in harmony with the low phosphorus content. Barnes (1939b) reported schreibersite and presented photomicrographs of it ; this is, however, a misinterpretation of the kamacite needles just described.

Troilite is common in all sizes, from 2 J.1 up to 3 mm. Most of the larger inclusions are rather spherical, while the smaller may be round, bar-shaped or plate-shaped. The troilite is monocrystalline and displays lenticular pointed twins due to plastic deformation. Daubreelite covers 5-20% of the troilite inclusions as parallel lamellae that range from 1-100 J.1 in size. In several inclusions the daubreelite

Figure 1280. Nordheim (Los Angeles). A rhomboid nodule com­posed of troilite (dark) with fine daubreelite lamellae (light). A thin taenite rim is still in contact with the sulfides. Etched. Scale bar 50 ll·

Figure 1281. Nordheim (U.S.N.M. no. 3190). Another troilite­daubreelite nodule, under crossed pollars. The daubreelite is dark; the troilite, light and displays multiple twinning. Etched. Scale bar 100 ll· S.I. neg. 1449B.

lamellae have been sheared and bent gently by plastic deformation. The troilite has a microhardness of 270±20, the daubreelite, of about 350.

Kamacite has been nucleated irregularly upon the sulfide inclusions. A rim of kamacite, 30-50 J.1 wide, around part of the larger inclusions is very common. Only occasionally have a-lamellae started to grow from these rims in a Widmanstiitten pattern. Where kamacite has not nucleated, a 2-10 J.1 thick shell of solid taenite is still in direct contact with the sulfides.

Nordheim is an ataxite which structurally and chem­ically is unrelated to the ataxites of group IVB. It is further different from Del Rio, Tucson and Monahans which have the same approximate nickel content; it resembles Guffey in some respects.

Specimen in the U.S. National Museum in Washington:

1 ,094 g slice (no. 3190, 13 x 9 x 3 em)

Norfolk, Virginia, U.S.A.

36°54'N, 76° I8'W

Medium octahedrite, Om. Bandwidth 1.00±0.15 mm. Distorted e-structure. HV 305± 15.

Group IliA. 7.48% Ni, 0.49% Co, < 0.1% P, 21 ppm Ga, 38 ppm Ge, 10.5 ppm Ir.

HISTORY

The history of this 23 kg mass is obscure. According to Mac Naughton (I 926) and Reeds (I 937: 604), the meteor­ite was observed to fall in 1906, but, as pointed out by Nininger (1937a) and others, this is out of the question. It is not known where it was found. Reeds (op.cit.) stated that it was exhibited at the Jamestown (Virginia) Exposi­tion in 1907 by Dr. E.A. :Shubert of Virginia. It was again exhibited in Pittsburgh, Pennsylvania, in 1910, 1911 and 1912. By 1923 when the meteorite was acquired by the American Museum of National History, it had been cut into two pieces of 21.6 kg and I ,275 g. The smaller piece was exchanged with Ward's Natural Science Establishment

'1 1111111 "1"''1""1''''1' II 1111 II I II 11 111 ''1' II '1 11111111

Figure 1282. Norfolk (Tempe no. 410.3) A 33 g part slice showing the distorted and indistinct Widmanstiitten structure. A deformed troilite-<laubreelite lens (dark) is also seen. Deep-etched. Scale in centimeters. (Courtesy C.B. Moore.)

where it was subdivided and offered for sale in the thirties (Ward's Price Lists No . 342, 193I; 1938; 1940). All that can be concluded at this late date is that Norfolk presumably was found in coastal Virginia about 1906 and that the early possessors, to make it more attractive, attached an imaginary story of an observed fall. It may, of course, also have been discovered accidentally when actual­ly hunting for some observed fireball "that landed right across those fences," as is so often believed by inexperi­enced observers.

Wiik & Mason (1965) presented a new analysis. Jaeger & Lipschutz (1967b) interpreted the kamacite structure as due to shock in the 130-400 k bar region. Fireman & Schwarzer (1957) examined the 3 H and 3 He amounts. Schaeffer & Heymann (1965) found no 39 Ar activity (half life 270 years), indicating that the fall took place consider­ably more than 1,000 years ago. The cosmic ray exposure age was estimated to be 600±60 million years. Lipschutz et al. (1965) came to the same exposure age, while Voshage (1967) by the 4<1<.j41K method found 685±55 million years. Noble gas data were presented by Hintenberger et al. (1967).

COLLECTIONS

New York (20.9 kg main mass and 338 g slice), Harvard (200 g), Chicago (145 g), Washington (110 g), Los Angeles (99 g), London (90 g), Tempe (33 g).

DESCRIPTION

The specimen in the U.S. National Museum is weath­ered with up to 2 mm thick, limonitic crusts locally. The troilite inclusions are veined by pentlandite. The heat­affected zone is, however, preserved in many places as an up to 1 mm thick rim of finely granulated o: 2 • The grain size is rather small, 20-50 11 across, as it usually is when formed from a shock-hardened E-structure. The microhard­ness is 190±10.

Norfolk is a medium octahedrite with undulating, long (W ~ 25) kamacite lamellae with a width of I.OO±O.I5 mm. While the parent crystal, no doubt, was a single undeformed austenite crystal the present Widmanstatten structure is severely distorted, indicating that significant plastic defor­mation took place after the 'Y ~ o: transformation was completed. The kamacite is of the contrast-rich, cross­hatched E-type, associated with shocks, and its microhard­ness is 305±15. There is a smooth hardness gradient from I90 in the rim zone to 305 in the interior which is met with at a depth of 6-10 mm (hardness curve type I).

Norfolk 9I3

Taenite and plessite cover about 35% by area, mostly as degenerated comb and net plessite with discontinuous taenite borders. The taenite is dark-etching in the interior, but yellowish in the rim zone where the temperature briefly rose above 1000° C, thereby allowing carbon to diffuse away. The larger taenite wedges of the interior have martensitic transition zones and a fine-grained, duplex o: + 'Y center.

Schreibersite is only present as scattered, 2-10 J1 wide grain boundary veinlets and as an occasional 5 J1 bleb precipitated upon the troilite nodules. A few I J1 rhabdites

Figure 1283. Norfolk (Tempe no. 410.3). Cloudy taenite with severe kneading. Shock-hatched kamacite with three distorted carlsbergite platelets. The central one has nucleated small rhabdite crystals. Etched. Oil immersion. Scale bar 20 IL·

.. Figure 1284. Norfolk (Tempe no. 410.3). A cloudy taenite lamella showing violent deformation. Shock-hatched kamacite on either side. Etched. Oil immersion. Scale bar 20 IL ·

NORFOLK - SELECTED CHEMICAL ANALYSES

percentage I

ppm

References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Wiik & Mason 1965 7.5I 0.65 Cobb I967 0.49 I I63 2I II

Wasson & Kimberlin I967 7.45 I 20.2 38.1 10

914 Norfolk - Norfork

occur in some kamacite lamellae. The bulk phosphorus content is estimated to be about 0.08-0.09%.

Troilite is rather common as 0.05-5 mm angular or rounded bodies which usually contain about 15% daubree­lite in the form of parallel, narrow lamellae. The troilite was once monocrystalline, but, as a result of the plastic deformation mentioned above, it is now severely brecciated and shows undulatory extinction or martensitic lenticular deformation twins. It is frequently sheared and displaced in successive steps, each 50-100 f.1 wide, but it is not shock­melted. Also present are small, 20-100 f.1 crystals showing rhythmic intergrowth of alternating 1 f.1 wide troilite and daubreelite lamellae.

Chromite occurs as 100-500 f.1 euhedric crystals, some of which have served as nucleation centers for troilite and for a minute quantity of phosphides. The troilite may have decomposed later to form some daubreelite and in these cases chromite and daubreelite are found in intimate contact. The aggregates are usually crushed by the plastic flow of the surrounding metal.

In the kamacite matrix are numerous hard, 20 x 1 f.l, platelets of carlsbergite.

Norfolk is a weathered medium octahedrite which is structurally and chemically closely related to Boxhole, Hen bury, Costilla Peak and other irons of the phosphorus­poor end of group IliA.

Specimen in the U.S. National Museum in Washington:

110 g part slice (no. 1294, 9 x 3.5 x 0.7 em)

Norfork, Arkansas, U.S.A.

36°13'N,92°17'W; 150m

Medium octahedrite , Om. Bandwidth 1.05±0.15 mm. Neumann bands. HV 250± 15.

Group lilA . 7.92% Ni, 0.50% Co, 0.14% P, 20.4 ppm Ga, 41.2 ppm Ge, 0.3 ppm Ir.

HISTORY

A mass of unknown weight fell in October 1918 near Norfork, Baxter County. Isaac C. Luther allegedly saw it fall. While searching for a large mass next day, he only located a fragment of 1 ,050 g which was recovered from a 120 em deep hole. Unfortunately, very little detailed

information was available when Nininger in the mid-thirties learned about the fall. The finder had been dead for several years and the community seemed to have no recollection whatsoever of the fall. Nininger (1937a) described the fragment and gave three photographs but was unable to locate the remaining, probably larger, mass. La Paz (1938) discussed the unusually deep impact hole of the small body. Nininger & Nininger (1950: plate 17) gave a photograph of the well-preserved exterior. Jaeger & Lipschutz (1967b) found the kamacite to be shocked between 130 and 400 k bar. Fireman & Schwarzer (1957) examined the 3 He, 3 H and 6 Li isotopes. Tilles & Tamers ( 1963) discussed the reasons for tritium being lower than expected in Norfork and other iron meteorites. Schaeffer & Heymann (1965) counted 3~1, 39 Ar and 311Ar and found an exposure age of 690-700 million years. Voshage ( 1967) estimated the exposure age to be 700±80 million years. Hintenberger et al. (1967a) measured the concentration of the noble gases. In these works it was assumed that the mass of the fall was only 1 kg; it is, however, almost certain that a considerably larger body fell but only 1 kg was recovered. The coordinates above are those of Norfork.

COLLECTIONS

Tempe (481 g), London (97 g) , Washington (60 g), Los Angeles (9 g).

Figure 1285. Norfork (Tempe no. 296.1). The recovered mass shows distinct regmaglypts and well-preserved fusion crusts. Scale bar approximately 2 em.

NORFORK - SELECTED CHEMICAL ANALYSES

Berkey & Fisher (1967) mapped the chlorine distribu­tion of a 2 cm2 slice adjacent to the surface. The chlorine ranged. from 0.05 to 2 ppm, a range similar to that for the

percentage References Ni Co p c Wasson & Kimberlin

1967 7.88 Moore et al. 1969 7.95 0.50 0.14 20

other falls examined, but 10 to 104 times lower than for weathered finds.

ppm , s Cr Cu Zn Ga Ge Ir Pt

20.4 41.2 0.3 70 170