Strontium Minerals

Joyce A. Ober

INTRODUCTION

Strontium occurs commonly in nature, averaging 0.034% of all igneous rock, and is the

15th most abundant element in the earth's crust. Only two minerals, however—celestite,

or celestine (strontium sulfate, SrS04), and strontianite (strontium carbonate, strontium

in suffcient quantities to make recovery practical, and these minerals are found

predominantly in sedimentary rocks. Of the two, celestite is more common in economic

deposits. It is similar in structure to barite, the barium sulfate mineral. Strontianite is

more desirable of the two common minerals because strontium•is used most commonly

in the carbonate form and contains more-strontium, but few deposits have been

discovered that are suitable for economic development. Table I lists the properties of

celestite and strontianite. In 2003, celestite production was reported in Argentina, Iran,

Mexico, Morocco, Pakistan, Spain, and Turkey (Ober 2004).

Although large deposits have been identified in these and other countries, detailed

descriptions of the deposits and locations are not available. Nearly all celestite is

converted to strontium carbonate, which may be used as-is or converted into other

strontium compounds, including strontium chloride, chromate, nitrate, oxalate, oxide,

and peroxide. nie largest end use for strontium is in faceplate glass for

cathode-ray tubes (CRTs) such as is used in televisions and computer monitors.

Probably the oldest use for strontium is in pyrotechnics such as fireworks, signal flares,

and tracer ammunition, because strontium compounds burn with a brilliant crimson

flame; strontium nitrate and peroxide are the most common strontium compounds used

in pyrotechnics. Iülese and other strontium compounds are used in lesser quantities in

ceramics and glass, permanent ferrite magnets, paint, and toothpaste for temperature

sensitive teeth. MAOR DEPOSITS AND PRODUCTION Although the average

strontium content of sedimentary rocks is less than in igneous rocks, nearly all

commercial operations are in sedimentary deposits. niese sedimentary deposits

(primarily as celestite) formed in lakes and lag«ns by replacement of preexisting clastic

sediments and fr«luently occur as beds or lenses with gypsum, anhydrite, or halite. niis

of deposit in Iran, Mexico, Spain, the United Kingdom, and the United States.

Hydrothermal strontium mineral deposits have been found in Russia

and the United States. Infiltration deposits that can be predominantly

Table 1. Physical properties of strontium minerals

PROPERTY

Chemical formula

Crystal structure

Cleavage

Color

Flame color

Fracture

Hardness

Index of refraction

Luster

Solubility

Specific gravity

Streak

Theorectical strontium content

Transparency

CALESTITE

SrSO4

Dipyramidal orthorhombic, tabular.

Sometimes fibrous and granular.

Perfect basal and prismatic

Primarily white to grayish blue.

Sometimes shades of yellow and red.

Crimson

Uneven

3.0-3.5

1.622-1.631

Vitreous, pearly on cleavage

Insoluble

3.9-4.0

White

47.6%

Translucent to opaque. Rarely, nearly

transparent.

Strontianite

SrC03

Dipyramidal orthorhombic.

Radiating, columnar, fibrous, or

granular.

Imperfect prismatic

Primarily white or grayish white.

Sometimes pole green or yellowish.

Crimson

Conchoidal

1.520-1.667

Vitreous

Effervescent in hydrochloric acid

3.6-3.8

White

59.3%

Translucent to transparent.

celestite or strontianite appear as geodes in calcite, celestite veins in clays and carbonate rocks, and metasomatic bodies in carbonate rocks. One deposit of this type is identified near Münster, Germany. Volcanic—sedimentary deposits are associated with rhyolites, andesites, basalts, and their tuffs and tuffites. Strontianite is believed to be a secondary mineral formed through the weathering of celestite (Hartrn and Kuivart 1996). United States Although celestite deposits have been identified nationwide, domestic production has been very limited. During World War Il, was mined in California and Texas. Since 1959, alldemand has been met from foreign sources. Only one U.S. company, Chemical Products Corporation (CPC), produces strontium cartxnate—by far, the most important strontium compound. CPC uses die black ash method to convert imported Mexican celestite to carbonate production at its 22-ktpy plant in Cartersville, Ge«gia. nie company also produces strontium nitrate. A few companies produce other minor strontium compounds from strontium carbonate. Mallinkrodt Inc. of St. Louis, Missouri, proåres strontium chloride, and Laporte Pigments Corp. of Belts Ville, Maryland, produces strontium chromate. Other companies produe smaller quantities of other downstream strontium compounds. In 1944, domestic strontium deposits were operated at the following sites: near Blanket in Brown County, Texas; in Nolan County, Texas; in fish Mountains in Imperial County, California; and near Ludlow, California (Gwinn 1944).At that time, the major use for Arontium chemicals was for pyrotechnic applications such as signal flares and tracer bullets required for military applications. Imme- diaeåy following World War Il, this demand dramatically decreased, in reducea•domestic production of celestite. Resources in the United States have been estimated at 3.2 Mt with an identified reserve base of 1.4 Mt. The reserve base figure inclu&s material containing no more than 60% strontium sulfate, a mua lower grade than by modern consumers. In addition to mined in the early 1940s, celestite has been discovered in Arizona, Arkansas, Kentucky, Michigan, Missouri, New York, Oh.b, Pennsylvania, Tennessee, Utah, and Washington (Schreck and Arundale 1959).

Other CountriesHuge deposits of high-grade celestite have been discovered throughout the world. In almost all instances, celestite deposits occur far from population centers in remote, undeveloped locations whae inexpensive labor is available for mining. World celestite production is listed in Table 2. Detailed information on most world resources is not readily available. Many of the large deposits are in remote, sparsely inhabited areas, where very little exploration has occurred. Other known deposits are in countries where specific mineral information is not easily obtained. Two types of strontium capacity exist. The first is ore production apacity in which celestite is mined and beneficiated for use or additional processing. second, strontium compound production capacity, represents the size of the operations that convert strontium mirrrals (almost always celestite) through chemical reactions to other forms of strontium, including strontium carbonate and strontium metal. Strontium compound capacity is deemed the more important for several reasons. Essentially, all strontium is conin compound form, primarily as the carbonate and to a lesser extent as the nitrate. Strontium carbonate is also the intermediate product in production of downstream compounds. At least nine countries mined celestite in 2003, as shown in Table 2.

Table 2. Celestite: World production by country

Country 1999 2000 2001 2002 2003Argentina Iran* Mexico Morocco Pakistan Spain Turkey

Total

2,141 1,650164,682 0634 128,457 60,540

358,000

4,656 2,000 157,420 7,539 1,918 148,352 24,150

346,000

2,440 2,000 I45,789 1,8792,000 129,794 63,635

348,000

3,106 2,000 94,015 3,780 2,000160,519 70,000 335,000

3,323 2,000 126,747 2,700 2,000 160,00070,000

367,000

Virtually all of the celestite mined annually is in the production of strontium carbonate and other strontium Very little strontium was consumed directly in the form. Because most ore is produced for market by means of vay simple sorting and beneficiation techniques, capacity can easily raised to meet increased demand. Strontium cartnnate production capacity is the limiting factor in strontium production, requiring more complicated and sophisticated processing facilities. strontium carbonate production capacity listed in Table 3 was compiled from reports cited in the following specific country sections. Algeria Celestite was mined in Algeria from the Beni Mangour surface deposit near Boira, although no production has been reported since at least 1996. The deposit was mined by Enterprise Nationale des Produits Non Ferreux et des Substances (ENOF) and was controlled by L' Enterprise National de Developpement Miniéres (SONAREM). In the past, as much as 3.6 ktpy was exported to nations in Eastern Europe and the forma Federal Republic of Germany. Although the celestite was relatively lowgrade only about 70% strontium sulfate—it contained low concentrations of barite, silica, gypsum, and iron, making it possible to concentrate the ore to acceptable levels using only gravity separation (Anon. 1988a). Reported reserves at Beni Mancour were more than 6 Mt of 70% strontium sulfate. ENOF was considering new production from the deposit to supply a possible domestic strontium carbonate plant whose output would be exported (Senouci, Nadir, and Houssa 2000). Argentina Although not a major producer of celestite, some is mined in Argentina. Little information about the Argentine strontium industry, other than production data, has been published for several years (Torres When detailed information was last reported in 1988, celestite mining was controlled by the Argentine Mining Union at the San Juan mine in the province of Mendoza Celestite was identified at a few additional small mines, the Maria Del Carmen and Don Luis mines. also in Nlendoza Province, and the Rayoso. Julio. Cerro Partido. and Llao mines in the province of