Celestite

Sulfur occurs native in the vicinity of volcanos and hot springs. It is widely distributed in nature as iron pyrites, galena, sphalerite, cinnabar, stibnite, gypsum, epsom salts, celestite, barite, etc. 

Strontium is found chiefly as celestite and strontianite. The metal can be prepared by electrolysis of the fused chloride mixed with potassium chloride, or is made by reducing strontium oxide with aluminum in a vacuum at a temperature at which strontium distills off. Three allotropic forms of the metal exist, with transition points at 235 and 540oC. 

Occurrence. The principal strontium mineral is celestite, naturally occurring strontium sulfate. Celestite and celestine [7759-02-6] both describe this mineral. However, celestite is the form most widely used in Knglish-speaking countries. Celestite has a theoretical strontium oxide content of 56.4 wt %, a hardness of 3—3.5 on Mohs scale, and a specific gravity of 3.96. It is usually white or bluish white and has an orthorhombic crystal form. 

Deposits of celestite in Gloucestershire, the United Kingdom, represented the main source of the world supply from 1884 to 1941 and provided up to 90% of the world strontium supply (4). During World War II, shipments to the United States and Western Europe from the United Kingdom were dismpted, and celestite deposits in Mexico and Spain were developed. 

Strontium has a valence of +2 and forms compounds that resemble the compounds of the other alkaline-earth metals (see Barium compounds Calcium compounds). Although many strontium compounds are known, there are only a few that have commercial importance and, of these, strontium carbonate [1633-05-2] SrCO, and strontium nitrate [10042-76-9], Sr(N03)2, are made in the largest quantities. The mineral celestite [7759-02-6], SrSO, is the raw material from which the carbonate or the nitrate is made. 

There are two main processes for conversion of celestite, ie, strontium sulfate, to strontium carbonate. The principal process is the black ash process. Strontium nitrate is produced by dissolving celestite in nitric acid and purifying it. Most other strontium compounds are produced from strontium nitrate. To service this market, NOAH Technologies Corporation (San Antonio, Texas) has estabUshed a plant in Mexico to manufacture most commercial- and reagent-grade strontium compounds except strontium carbonate. 

Economic Aspects. Celestite is mined and then shipped to countries where chemical processing takes place. Spain is the largest celestite-exporting country, as almost all of its output is exported. Mexico is the next largest exporter. About half of its annual output is exported. Most of celestite production from Turkey and Iran is also exported. Iranian exports are beheved to be shipped to the CIS and other Eastern European countries. 

Production. In the commercial production of strontium carbonate, celestite ore is cmshed, ground, and stored in bins before it is fed to rotary kilns. As the ground ore is being conveyed to the kilns, it is mixed with ground coke. In the kilns, the celestite is reduced to strontium sulfide [1314-96-1J, known as black ash, according to the reaction ... 

Strontium Oxide, Hydroxide, and Peroxide. Strontium oxide, SrO, is a white powder that has a specific gravity of 4.7 and a melting point of 2430°C. It is made by heating strontium carbonate with carbon in an electric furnace, or by heating celestite with carbon and treating the sulfide formed with caustic soda and then calcining the product (10). It reacts with water to form strontium hydroxide [18480-07-4] and is used as the source of strontium peroxide [1314-18-7],... 

Strontium Sulfate. Strontium sulfate, SrSO, occurs as celestite deposits in beds or veins in sediments or sedimentary rocks. Celestite has a specific gravity of ca 3.97, a Mohs hardness of 3.0—3.5, and is colodess-to-yeUow and often pale blue. Strontium sulfate forms colorless or white rhombic crystals with a specific gravity of 3.96 and an index of refraction of 1.622—1.631. It decomposes at 1580°C and has a solubiUty of 0.0113 g per 100 mL of water at 0°C. 

Celestite, Mineral Dossier No. 6, Mineral Resources Consultative Committee, HMSO, London, 1973. 

Carbonates and Sulfates Carbonates include limestone, cal-cite, marble, marls, chalk, dolomite, and magnesite the most important sulfates are barite, celestite, anhydrite, and gypsum these are used as fillers in paint, paper, and rubber. (Gypsum and anhydrite are discussed below as part of the cement, lime, and gypsum industries.)... 

The elements Na, K, Cl, SO, Br, B, and F are the most conservative major elements. No significant variations in the ratios of these elements to chlorine have been demonstrated. Strontium has a small (< 0.5%) depletion in the euphotic zone (Brass and Turekian, 1974) possibly due to the plankton Acantharia, which makes its shell from SrS04 (celestite). Calcium has been known since the 19th century to be about 0.5% enriched in the deep sea relative to surface waters. Alkalinity (HCOf") also shows a deep enrichment. These elements are controlled by the formation... 

Blount, C.W. (1974) Synthesis of barite, celestite, anglesite, witherite, and strontianite from aqueous solutions. Am. Min., 59, 1209-1219. 

B. Marino, J. J. Boon, E. Hendricks, F. Horreard and F. Hillion, Imaging ToF SIMS and NANOSIMS studies of barite celestite particles in grounds from paintings by Van Gogh, e Preservation... 

Strontium sulphate (celestite) Exoskeletons of a few marine organisms... 

A common problem in offshore petroleum production is that sulfate scale may form when seawater is injected into the formation during waterflooding operations. The scale forms when seawater, which is rich in sulfate but relatively poor in Ca++ and nearly depleted in Sr++ and Ba++, mixes with formation fluids, many of which contain bivalent cations in relative abundance but little sulfate. The mixing causes minerals such as gypsum (CaSC>4 2H2O), anhydrite (CaSC>4), celestite (SrSOzO, and barite (BaS04, an almost insoluble salt) to become saturated and precipitate as scale. 

The Amethyst fluid is richer in strontium and calcium than the other fluids, but nearly depleted in barium. Celestite becomes saturated first, and more of this mineral forms from this fluid than from the Forties fluid. Anhydrite becomes saturated later in the mixing process and precipitates,... 

In the three simulations, the sulfate minerals form at mixing ratios related to their solubilities. Barite, the least soluble, forms early, when small amounts of seawater are added. The more soluble celestite forms only after the addition of somewhat larger quantities of seawater. Anhydrite, the most soluble of the minerals, forms from the Amethyst fluid at still higher ratios of seawater to formation fluid. 

Occurrence. Strontianite (SrC03) and celestite (SrS04) are the only minerals of economic importance. 

Major structural components of hard parts Ca, C, SI, 0, P, F, Sr, S Calcite, aragonite, opaline silica, celestite, apatite, fluoroapatite Components of frustules and tests, bone, teeth... 

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