cassiterite

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cassiterite

(kəsĭt`ərīt), heavy, brown-to-black mineral, tin oxide, SnO2, crystallizing in the tetragonal system. It is found as short prismatic crystals and as irregular masses, usually in veins and replacement deposits associated with granites. Since it is hard, heavy, and resistant to weathering, it often concentrates in alluvial deposits derived from cassiterite-bearing rocks. It is the principal ore of tin and is mined in many countries; the most important sources are Malaysia, Thailand, China, Indonesia, Bolivia, and Russia. Except for Bolivia, nearly all of this production is from alluvial deposits.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Cassiterite

 

(or tinstone), a mineral with the chemical composition Sno2. Theoretically it contains 78.62 percent Sn but usually includes impurities of Nb, Ta, Zr, Sc, W, and Fe; thus, the Sn content varies within 68–78 percent.

Cassiterite crystallizes in the tetragonal system, forming prismatic or dipyrimidal crystals. Geniculated twins are characteristic. The crystalline structure is analogous to that of rutile. Cassiterite is usually encountered in the form of small and large crystals, drusoid aggregates, or compact granular masses as well as in the form of cryptocrystalline, colloform segregations, concretions, and sinter formations. The color is dark brown, almost black, yellow with a reddish brown cast; nearly colorless varieties are also known. Cassiterite has an adamantine luster, a hardness of 6–7 on the mineralogical scale, and a density of 6, 040–7, 120 kg/m3 (lowest in light-colored cassiterite).

The deposits are usually genetically linked with granitic rocks. The most interesting commercial accumulations of the mineral are characteristic for hydrothermal quartz-cassiterite and sulfide-cassiterite veins. Cassiterite is stable in zones of oxidation and surface weathering; with the destruction of primary deposits, it accumulates in placers. In the USSR, cassiterite deposits are found in the northeast in Primor’e, in Middle Asia, and in the Kazakh SSR. Abroad, it is found in Malaysia, Thailand, Indonesia, the People’s Republic of China, Bolivia, Nigeria, and elsewhere. Cassiterite is the chief ore for obtaining tin.

A. B. PAVLOVSKII

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

cassiterite

[kə′sid·ə‚rīt]
(mineralogy)
SnO2 A yellow, black, or brown mineral that crystallizes in the tetragonal system in prisms terminated by dipyramids; the most important ore of tin. Also known as tin stone.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Pegmatites from which the cassiterite has been commercially exploited are located on the farms Davib Ost 61, Sandamap, Ameib 60, Onguati 52 and Brabant 68; the latter three are closely related spatially to the Erongo Granite (Diehl, 1992a).
Over 70 years ago, Gevers and Frommurze (1930) observed that black iron-rich tourmaline (schorl) "frequently in large, well-formed crystals" is characteristic only of the non-tin-bearing pegmatites, which explains why cassiterite has not typically been found associated with the minerals that have been collected over the past few years.
This was a polymetallic deposit with ferberite and minor cassiterite accompanied by fluorite, beryl and minor molybdenum, iron and copper sulfides.
There are several ferberite, cassiterite, tantalite and beryl occurrences in the vicinity of the mine, but historical mining operations tended to focus on the tungsten deposits on Krantzberg hill (Schlogl, 1984).
Cassiterite and ferberite were discovered in alluvial gravels during the late 1920's.
Accessory minerals are biotite, calcite, cassiterite, chalcopyrite, chlorite, ferberite, goethite, titanite, zircon, bismuth, powellite, scheelite and minor sulfides such as arsenopyrite, pyrite and molybdenite (Schlogl, 1984).
Fine-grained, almost invisible disseminations of cassiterite are virtually ubiquitous at Cerro Rico, and currently constitute the main ore mineral (Ahlfeld and Reyes, 1955; Jaskolski, 1933).
As an early-stage hydrothermal mineral, chalcopyrite is rare in the upper levels but common in the deeper levels, where it occurs associated with stannite, cassiterite and arsenopyrite.
Earthy goethite is the primary component of the limonitic cassiterite ore found in the upper parts of the Cerro Rico.
The mineral also constitutes a component of the limonitic cassiterite ore, and forms druses of small crystals lining feldspar-shaped vugs in dacite.
Ahlfeld and Reyes (1955) report that miargyrite was once abundant in the upper portions of the Tajo Polo vein system, as compact masses in pyrite with associated pyrargyrite and cassiterite. The recently discovered Potosi vein is producing complex, lustrous, 4-mm to 5-mm crystals associated with crystals of diaphorite, pyrostilpnite and pyrargyrite, in vugs in massive pyrargyrite and miargyrite.
Ahlfeld and Reyes (1955) reported pyrargyrite/miargyrite intergrowths, often intimately mixed with cassiterite, to be locally abundant in the upper levels of the Tajo Polo, Rica, and other veins.