literatur leucite
TRANSCRIPT
Definition of LEUCITE
: a white or gray mineral consisting of a silicate of potassium and aluminum and occurring in
igneous rocks
THE MINERAL LEUCITE
Chemistry: KAlSi2O6, Potassium Aluminum Silicate Class: Silicates Subclass: Tektosilicates Group: Feldspathoids Uses: mineral specimen and as a minor source of
potassium and aluminum. Specimens
Leucite is a popular and interesting mineral. Its name comes from the greek word for "white" in allusion to its typical color. At high temperatures, leucite is isometric and will form the isometric trapezohedron crystal form. Interestingly, as leucite cools, the isometric structure becomes unstable and transforms into a tetragonal structure without altering the outward shape. Although the mineral is actually tetragonal, the outward shape is pseudo-isometric and thus the crystal form is actually pseudo-trapezohedral.
Leucite is one of the few minerals that forms the unique trapezohedron. The trapezohedron has 24 deltoid shaped faces, where each face occupies one third of the position of a single octahedron's face. The minerals of the garnet group and the mineral analcime are the only common minerals that will also form the trapezohedron.
Distinguishing leucite from the garnets and analcime is relatively easy in some cases. The garnets are much harder and usually
deeply colored. Leucite has a much lower density and usually has a duller luster than analcime. Also leucite is typically embedded in host rock where as analcime, when displaying good crystals and not massive or granular, is loose or attacted to other minerals in volcanic cavities.
Leucite, KAlSi2O6 is actually distantly related to analcime, NaAlSi2O6-H2O. Leucite is a member of the feldspathoid group of minerals. Analcime, although usually considered azeolite, is sometimes placed in the feldspathoid group since its chemistry and occassional occurrences are similar.
Minerals whose chemistries are close to that of the alkali feldspars but are poor in silica (SiO2) content, are called feldspathoids. Leucite, like other feldspathoids, is found in silica poor rocks containing other silica poor minerals and no quartz. If quartz were present when the melt was crystallizing, it would react with any feldspathoids and form a feldspar..
At one time leucite was used as a source of potassium and aluminum. Probably due to the high aluminum to silicon ratio, its structure is easily destroyed by acids and this frees the aluminum ions.
Leucite, already a pseudomorph from a high temperature phase, commonly is altered to pseudoleucite. Pseudoleucite is not a mineral but a mixture of nepheline, orthoclaseand analcime.
PHYSICAL CHARACTERISTICS:
Color is clear, white or gray, with yellowish and reddish tints possible.
Luster is vitreous or greasy to dull. Transparency: crystals are transparent, translucent to
commonly opaque. Crystal System is isometric; 4/m bar 3 2/m at temperatures
above 605 degrees C, and tetragonal; either 4 2 2 or 4/m, below 605 degrees C.
Crystal Habits include the characteristic trapezohedron (actually pseudo-trapezohedron). Also granular and massive.
Cleavage is absent.
Fracture is conchoidal Hardness is 5.5 - 6. Specific Gravity is approximately 2.4 - 2.5 (slightly below
average) Streak is white. Associated
Minerals include olivine, labradorite, augite, biotite, nepheline and other feldspathoids.
Other Characteristics: surface is usually pitted, dull or has a weathered look.
Notable Occurrences include Mt. Vesuvius, Italy; Magnet Cove, Arkansas, Leucite Hills, Wyoming and Litchfield, Maine, USA; Brazil and Hastings Co, Ontario.
Best Field Indicators are crystal habit, density, low hardness, luster and associations.
http://www.galleries.com/Leucite
General Leucite Information Chemical Formula: KAlSi2O6
Composition: Molecular Weight = 218.25 gm
Potassium 17.91 % K 21.58 % K2O
Aluminum 12.36 % Al 23.36 % Al2O3
Silicon 25.74 % Si 55.06 % SiO2
Oxygen 43.99 % O
______ ______
100.00 % 100.00 % = TOTAL OXIDE
Empirical Formula: KAl(Si2O6)
Environment: Acid volcanic rocks.
IMA Status: Valid Species (Pre-IMA) 1791
Locality: Bearpaw Mountains., Montana, USA. Link to MinDat.org Location Data.
Name Origin: From the Greek leukos - "white."
Name Pronunciation: Leucite
Synonym: Amphigene
Leucite Image Images: Leucite
Comments: Large single crystal of dark gray leucite.Location: Roccamonfina, Caserta Province, Campania, Italy. Scale: 20x20x20 mm.© John Betts - Fine Minerals
Leucite Crystallography Axial Ratios: a:c = 1:1.05042
Cell Dimensions: a = 13.09, c = 13.75, Z = 16; V = 2,356.04 Den(Calc)= 2.46
Crystal System: Tetragonal - DipyramidalH-M Symbol (4/m) Space Group: I 41/a
X Ray Diffraction: By Intensity(I/Io): 3.266(1), 3.438(0.85), 5.39(0.8),
Crystal Structure:
Mousedrag1 - LMB Manipulate Structuredrag2 - RMB Resize/RotateKeyboardS - Stereo Pair on/offH - Help ScreenI - Data InfoA - Atoms On/OffP - Polyhedra On/OffB - Bonds On/OffHelp on Above
Mazzi F , Galli E , Gottardi G , American Mineralogist , 61 (1976) p.108-115, The crystal structure of tetragonal leucite
View Additional jPOWD Structure files for Leucite[1] [2] [3] [4] [5] [6] [7] [8]
Physical Properties of Leucite Cleavage: {110} Indistinct
Color: Colorless, Gray, Yellow gray, White.
Density: 2.47
Diaphaneity: Translucent to transparent
Fracture: Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.
Habit: Crystalline - Coarse - Occurs as well-formed coarse sized crystals.
Hardness: 6 - Orthoclase
Luminescence: Non-fluorescent.
Luster: Vitreous (Glassy)
Magnetism: Nonmagnetic
Streak: white
Optical Properties of Leucite Gladstone-Dale: CI meas= -0.006 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.01 (Superior) - where the CI = (1-KPDcalc/KC)KPDcalc= 0.2072,KPDmeas= 0.2064,KC= 0.2052
Ncalc = 1.5 - 1.51
Optical Data: Isotropic, n=1.508-1.511.
Calculated Properties of Leucite Electron Density: Bulk Density (Electron Density)=2.44 gm/cc
note: Specific Gravity of Leucite =2.47 gm/cc.
Fermion Index: Fermion Index = 0.01Boson Index = 0.99
Photoelectric: PELeucite = 3.14 barns/electronU=PELeucite x electron= 7.67 barns/cc.
Radioactivity: GRapi = 255.81 (Gamma Ray American Petroleum Institute Units) Concentration of Leucite per GRapi unit = 0.39 (%)
Estimated Radioactivity from Leucite - barely detectable
Leucite Classification Dana Class: 76.02.02.01 (76)Tectosilicate Al-Si Framework
(76.02)Feldspathoids and related species
(76.02.02)Leucite group
76.02.02.01 Leucite KAlSi2O6 I 41/a 4/m
76.02.02.02 Ammonioleucite (NH4,K)AlSi2O6 I 41/a 4/m
Strunz Class: 09.GB.05 09 - SILICATES (Germanates)
09.G - Tektosilicates with Zeolitic H2O
09.GB -Chains of single connected 4-membered rings
09.GB.05 Ammonioleucite (NH4,K)AlSi2O6 I 41/a 4/m
09.GB.05 Analcime NaAlSi2O6•(H2O) P1 1
09.GB.05 Hsianghualite Ca3Li2Be3(SiO4)3F2 I 213 2 3
09.GB.05 Lithosite K6Al4Si8O25•(H2O) P 21 (pseudo ORTH) 2
09.GB.05 Leucite KAlSi2O6 I 41/a 4/m
09.GB.05 Pollucite (Cs,Na)2Al2Si4O12•(H2O) I a3d 4/m 3 2/m
09.GB.05 Wairakite CaAl2Si4O12•2(H2O) I2/a 2/m
Other Leucite Information References: NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990)
OPTIC PROP.(Mason68)
See Also: Links to other databases for Leucite :1 - Am. Min. Crystal Structure Database2 - Amethyst Galleries' Mineral Gallery3 - Athena4 - EUROmin Project5 - Ecole des Mines de Paris6 - GeoScienceWorld7 - Glendale Community College8 - Google Images9 - Google Scholar10 - Handbook of Mineralogy (MinSocAm)11 - Handbook of Mineralogy (UofA)12 - MinDAT13 - Mineralienatlas (Deutsch)14 - Minerals in Thin Section-University of North Carolina15 - Minerals in Thin Sections-Humboldt State16 - Online Mineral Museum17 - QUT Mineral Atlas18 - Ruff.Info19 - Tradeshop.com - The Rainbow of Gems20 - UCLA - Petrography Thin-Sections21 - WWW-MINCRYST
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Translate Leucite Mineral Data :
Ask about Leucite here :Ask-A-Mineralogist from the Mineralogical Society of AmericaMindat.org's Discussion GroupsOriginal Rockhounds Discussion GroupRockhounds Discussion Group on Yahoo GroupsMineral Discussion Forum from Fabre Minerals - also available in Español
Print or Cut-and-Paste your Leucite Specimen Label here :
Leucite
KAlSi2O6 Dana No: 76.02.02.01 Strunz No: 09.GB.05
Locality:
Notes:
http://webmineral.com/data/Leucite.shtml
Leucite : K(AlSi2O6)
Stradner Kogel, Wilhelmsdorf, Bad Gleichenberg, Styria, Austria
Grey Leucite-xl;+ Apatite(white needles), Diopside(green -"-);Picture width: ~10mm;Field collected /by: 2003/ReMi;Collection/photo: ReMi/ReMi
© ReMi Photo ID: 73509 View Count: 504
Leucite : K(AlSi2O6)
Cascata, Águas da Prata, São Paulo, Brazil
single leucite crystal. Size 2x1,5x1cm. Rafael Hernandes Corrêa-Silva Collection.
© Brhounds Photo ID: 45120 View Count: 498
Leucite : K(AlSi2O6)
Krušné Hory Mts (Erzgebirge), Karlovy Vary Region, Bohemia (Böhmen; Boehmen), Czech Republic
A 4cm single leucite crystal. Photo is made in 2005.
© 2005 S.Sayamov Photo ID: 34471 View Count: 693
Leucite : K(AlSi2O6)
Radešin Hill, Ústí nad Labem (Aussig), Ústí Region, Bohemia (Böhmen; Boehmen), Czech Republic
Field of view 5mm
© Petr Fuchs Photo ID: 65207 View Count: 442
Leucite : K(AlSi2O6)
Radešin Hill, Ústí nad Labem (Aussig), Ústí Region, Bohemia (Böhmen; Boehmen), Czech Republic
FOV 3mm
© Petr Fuchs Photo ID: 134600 View Count: 292
Leucite : K(AlSi2O6)
Lapanouse-de-Sévérac (slag locality), Aveyron, Midi-Pyrénées, France
Field of wiew: 1,5mmCollection & Photo: D.Journet
© D.JOURNET Photo ID: 340881 View Count: 163
Leucite : K(AlSi2O6)
Oberrotweil, Kaiserstuhl, Baden-Württemberg, Germany
Field of view: 6 mm
© mk Photo ID: 75180 View Count: 529
Leucite : K(AlSi2O6)
Emmelberg, Üdersdorf, Daun, Eifel, Rhineland-Palatinate, Germany
Field of view: 0.8x0.6 mm
© JDehove Photo ID: 8141 View Count: 3106
Leucite : K(AlSi2O6)
Emmelberg, Üdersdorf, Daun, Eifel, Rhineland-Palatinate, Germany
Leucite from the Emmelberg. Image width: 4 mm. Collection: Willi Schüller, Adenau. Photo: Fred Kruijen
© Fred Kruijen Photo ID: 359042 View Count: 148
Leucite : K(AlSi2O6)
Emmelberg, Üdersdorf, Daun, Eifel, Rhineland-Palatinate, Germany
Field of view: 1.5 x 1.2 mm
http://www.mindat.org/gallery.php?min=2465
LeuciteFrom Wikipedia, the free encyclopedia
Leucite
Leucite crystals in a rock from Italy
General
Category tectosilicates
Chemical formula K[AlSi2O6]
Strunz classification 9.GB.05
Crystal symmetry Tetragonal 4/m dipyramidal
Unit cell a = 13.056 Å, c = 13.751 Å; Z = 16
Identification
Color White to grey
Crystal habit Commonly as euhedral, pseudocubic crystals;
rarely granular, massive
Crystal system Tetragonal
Twinning Common and repeated on {110} and {101}
Cleavage Poor on {110}
Fracture Conchoidal
Tenacity Brittle
Mohs scalehardness 5.5 - 6
Luster Vitreous
Diaphaneity Transparent to translucent
Specific gravity 2.45-2.50
Optical properties Uniaxial (+)
Refractive index nω = 1.508 nε = 1.509
Birefringence δ = 0.001
References [1][2]
Leucite is a rock-forming mineral composed of potassium and aluminium tectosilicate K[AlSi2O6]. Crystals have
the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically
isotropic, and are therefore pseudo-cubic. Goniometric measurements made byGerhard vom Rath in 1873 led
him to refer the crystals to the tetragonal system. Optical investigations have since proved the crystals to be
still more complex in character, and to consist of several orthorhombic or monoclinic individuals, which are
optically biaxial and repeatedly twinned, giving rise to twin-lamellae and to striations on the faces. When the
crystals are raised to a temperature of about 500 °C they become optically isotropic and the twin-lamellae and
striations disappear, although they reappear when the crystals are cooled again. This pseudo-cubic character
of leucite is very similar to that of the mineral boracite.
The crystals are white or ash-grey in colour, hence the name suggested by A. G. Werner in 1701, from
'λευκος', '(matt) white'. They are transparent and glassy when fresh, albeit with a noticeably subdued
'subvitreous' lustre due to the low refractive index, but readily alter to become waxy/greasy and then dull and
opaque; they are brittle and break with a conchoidal fracture. The Mohs hardness is 5.5, and the specific
gravity 2.47. Inclusions of other minerals, arranged in concentric zones, are frequently present in the crystals.
On account of the color and form of the crystals the mineral was early known as white garnet. French authors
in older literature may employ René Just Haüy's name amphigène, but 'leucite' is the only name for this
mineral species that is recognised as official by the International Mineralogical Association.
[edit]Leucite rocks
Rocks containing leucite are scarce, many countries such as England being entirely without them. However,
they are of wide distribution, occurring in every quarter of the globe. Taken collectively, they exhibit a
considerable variety of types and are of great interest petrographically. For the presence of this mineral it is
necessary that the silica percentage of the rock should be low, since leucite is incompatible with
free quartz and reacts with it to form potassium feldspar. Because it weathers rapidly, leucite is most common
in lavas of recent and Tertiary age, which have a fair amount of potassium, or at any rate have potassium equal
to or greater than sodium; if sodium is abundant nepheline occurs rather than leucite.
In pre-Tertiary rocks leucite readily decomposes and changes to zeolites, analcite and other secondary
minerals. Leucite also is rare in plutonic rocksand dike rocks, but leucite syenite and leucite tinguaite bear
witness to the possibility that it may occur in this manner. The rounded shape of its crystals, their white or grey
color, and absence of planar cleavage make the presence of leucite easily determinable in many of these rocks
by inspection, especially when the crystals are large.
Pseudoleucite from São João Alkaline Massif, RJ, Brazil
"Pseudoleucites" are rounded areas consisting of feldspar, nepheline, analcite, &c., which have the shape,
composition and sometimes even the outward crystalline shape of leucite; they are probably pseudomorphs or
paramorphs, which have developed from leucite because this mineral is not stable at ordinary temperatures
and can be expected under favorable conditions to undergo spontaneous change into an aggregate of other
minerals. Leucite is very often accompanied by nepheline, sodalite or nosean; other minerals which make their
appearance with some frequency are melanite, garnet and melilite.
The plutonic leucite-bearing rocks are leucite syenite and missourite. Of these the former consists
of orthoclase, nepheline, sodalite, diopside andaegirine, biotite and sphene. Two occurrences are known, one
in Arkansas, the other in Sutherland, Scotland. The Scottish rock has been calledborolanite. Both examples
show large rounded spots in the hand specimens; they are pseudoleucites, and under the microscope prove to
consist of orthoclase, nepheline, sodalite and decomposition products. These have a radiate arrangement
externally, but are of irregular structure at their centres; it is interesting to note that in both rocks melanite is an
important accessory. The missourites are more mafic and consist of leucite, olivine, augite andbiotite; the
leucite is partly fresh partly altered to analcite, and the rock has a spotted character recalling that of the leucite-
syenites. It has been found only in the Highwood Mountains of Montana.
The leucite-hearing dike-rocks are members of the tinguaite and monchiquite groups. The leucite tinguaites are
usually pale grey or greenish in color and consist principally of nepheline, alkali feldspar and aegirine. The
latter forms bright green moss-like patches and growths of indefinite shape, or in other cases scattered acicular
prisms, among the feldspars and nephelines of the ground mass. Where leucite occurs, it is always euhedral in
small, equant, many-sided crystals in the ground mass, or in larger masses which have the same characters as
the pseudoleucites. Biotite occurs in some of these rocks, and melanite also is present. Nepheline decreases in
amount as leucite increases since the abundances of the two reflect the Na:K ratio of the rock. Rocks of this
group are known from Rio de Janeiro, Arkansas, Kola (in Finland), Montana and a few other places.,
In Greenland there are leucite tinguaites with much arfvedsonite, (hornblende) and eudialyte. Wherever they
occur they accompany leucite- and nepheline syenites. Leucite monchiquites are fine-grained dark rocks
consisting of olivine, titaniferous augite and iron oxides, with a glassy ground mass in which small rounded
crystals of leucite are scattered. They have been described from Czechoslovakia.
By far the greater number of the rocks which contain leucite are lavas of Tertiary or recent geological age.
Although these never contain quartz, butfeldspar is usually present, though there are certain groups of leucite
lavas which are non-feldspathic. Many of them also contain nepheline, sodalite, hauyne and nosean; the much
rarer mineral melilite appears also in some examples. The commonest ferromagnesian mineral
is augite (sometimes rich insodium), with olivine in the more basic varieties. Hornblende and biotite occur also,
but are less common. Melanite is found in some of the lavas, as in the leucite syenites.
The rocks in which orthoclase (or sanidine) is present in considerable amount are leucite-trachytes, leucite-
phonolites and leucitophvres. Of these groups the two former, which are not sharply distinguished from one
another by most authors, are common in the neighborhood of Rome. They are of trachytic appearance,
containing phenocysts of sanidine, leucite, augite and biotite. Sodalite or hauyne may also be present, but
nepheline is typically absent. Rocks of this class occur also in the tuffs of the Phlegraean Fields, near Naples.
The leucitophyres are rare rocks which have been described from various parts of the volcanic district of the
Rhine (Olbrck. Laacher See, etc.) and from Monte Vulture in Italy. They are rich in leucite, but contain also
some sanidine and often much nepheline with hauyne or nosean. Their pyroxene is principally aegirine or
aegirine-augite; some of them are rich in melanite. Microscopic sections of some of these rocks are of great
interest on account of their beauty and the variety of feldspathoid minerals which they contain.
In Brazil leucitophyres have been found which belong to the Carboniferous period.
Those leucite rocks which contain abundant essential plagioclase feldspar are known as leucite tephrites and
leucite basanites. The former consist mainly of plagioclase, leucite and augite, while the latter contain olivine in
addition. The leucite is often present in two sets of crystals, both porphyritic and as an ingredient of the ground
mass. It is always idiomorphic with rounded outlines. The feldspar ranges from bytownite to oligoclase, being
usually a variety of labradorite; orthoclase is scarce. The augite varies a good deal in chemnistry and optical
character, being green, brown or violet (suggesting high Na and Ti content), but it is rarely high enough in Na
and Fe to qualify as aegirine-augite or aegirine. Among the accessory minerals biotite, brown hornblende,
hauyne, iron oxides and apatite are the commonest; melanite and nepheline may also occur. The ground mass
of these rocks is only occasionally rich in glass. The leucite-tephrites and leucite-basanites of Vesuvius and
Somma are familiar examples of this class of rocks. They are black or ashy-grey in color, often vesicular, and
may contain many large grey phenocysts of leucite. Their black augite and yellow green olivine are also easily
observed in hand specimens. From Volcan Ello, Sardinia and Roccamonfina similar rocks are obtained; they
occur also in Bohemia, in Java, Celebes, Kilimanjaro (Africa) and near Trebizond inAsia Minor.
Leucite lavas from which feldspar is absent are divided into the leucitites and leucite basalts. The latter contain
olivine, the former do not. Pyroxene is the usual ferromagnesian mineral, and resembles that of the tephrites
and basanites. Sanidine, melanite, hauyne and perovskite are frequent accessory minerals in these rocks, and
many of them contain melilite in some quantity, The well-known leucitite of the Capo di Bove, near, Rome, is
rich in this mineral, which forms irregular plates, yellow in the hand specimen, enclosing many small rounded
crystals of leucite. Bracciano and Roccamonfina are other Italian localities for leucitite, and in Java, Montana,
Celebes and New South Wales similar rocks occur, The leucite basalts belong to more basic types and are rich
in olivine and augite. They occur in great numbers in the Rhenish volcanic district (Eifel, Laacher See) and in
Bohemia, and accompany tephrites or leucitites in Java, Montana, Celebes and Sardinia. The peperino of the
neighborhood of Rome is a leucitite tuff.
[edit]See also
Wikimedia Commons has
media related to: Leucite
ultrapotassic
Phonolite
Igneous rocks
[edit]References
1. ̂ Leucite on Mindat
2. ̂ Handbook of Mineralogy
http://en.wikipedia.org/wiki/Leucite
Leucite adalah mineral populer dan menarik. Namanya berasal dari kata yunani yang berarti "putih" dalam kiasan warna yang khas. Pada temperatur tinggi, leucite adalah isometrik dan akan membentuk bentuk kristal isometrik trapezohedron. Menariknya, apabila leucite mendingin, struktur yang isometrik menjadi tidak stabil dan berubah menjadi struktur tetragonal tanpa mengubah bentuk luar.
Meskipun sebenarnya mineral tetragonal, bentuk lahiriahnya adalah pseudo-isometrik dan dengan demikian bentuk kristal sebenarnya adalah pseudo-trapezohedral. Leucite adalah salah satu dari sedikit mineral yang membentuk trapezohedron unik. Trapezohedron memiliki 24 deltoideus berbentuk wajah, di mana setiap wajah menempati sepertiga dari posisi oktahedron satu wajah. Mineral dari kelompok garnet dan mineral analcime adalah satu-satunya mineral yang umum yang berbentuk trapezohedron.Membedakan leucite dari analcime garnet relatif mudah dalam beberapa kasus. Kelompok garnet jauh lebih kompleks dan biasanya sangat berwarna. Leucite memiliki kerapatan yang jauh lebih rendah dan biasanya memiliki luster daripada analcime yang kusam. Leucite, dengan rumus kimia KAlSi2O6 sebenarnya jauh berbeda dengan analcime, NaAlSi2O6-H2O. Leucite adalah anggota kelompok feldspathoid mineral. Analcime, walaupun biasanya dianggap sebagai zeolit, kadang-kadang ditempatkan dalam grup feldspathoid.Mineral kimia yang dekat dengan alkali feldspars tetapi miskin dalam konten silika (SiO2), disebut feldspathoids. Leucite, seperti feldspathoids lain, ditemukan dalam batuan yang mengandung silika miskin dan tidak ada kuarsa. Jika kuarsa hadir ketika lelehan tersebut mengkristal, hal tersebut akan bereaksi dengan membentuk feldspathoids dan feldspar . Pada suatu waktu leucite digunakan sebagai sumber kalium dan aluminium. Mungkin karena aluminium tinggi untuk rasio silikon, strukturnya mudah hancur oleh asam dan membebaskan ion aluminium.
http://aramadzgeo09.blogspot.com/2012/01/1.html
