cassiterite

{{Infobox mineral | name = Cassiterite | category = Oxide minerals | boxwidth = | boxbgcolor = | image = 4447M-cassiterite.jpg | imagesize = | caption = Cassiterite surrounded by muscovite, from Xuebaoding, Huya, Pingwu, Mianyang, Sichuan, China (size: 100 × 95 mm, 1128 g) | formula = SnO2 | IMAsymbol=Cst | molweight = | strunz = 4.DB.05 | system = Tetragonal | class = Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) | symmetry = P42/mnm | unit cell = a = 4.7382(4) Å, c = 3.1871(1) Å; Z = 2 | color = Black, brownish black, reddish brown, brown, red, yellow, gray, white; rarely colorless | habit = Pyramidic, prismatic, radially fibrous botryoidal crusts and concretionary masses; coarse to fine granular, massive | twinning = Very common on {011}, as contact and penetration twins, geniculated; lamellar | cleavage = {100} imperfect, {110} indistinct; partings on {111} or {011} | fracture = Subconchoidal to uneven | tenacity = Brittle | mohs = 6–7 | luster = Adamantine to adamantine metallic, splendent; may be greasy on fractures | refractive = nω = 1.990–2.010 nε = 2.093–2.100 | opticalprop = Uniaxial (+) | birefringence = δ = 0.103 | pleochroism = Pleochroic haloes have been observed. Dichroic in yellow, green, red, brown, usually weak, or absent, but strong at times | streak = White to brownish | gravity = 6.98–7.1 | density = | melt = | fusibility = infusible | diagnostic = | solubility = insoluble | diaphaneity = Transparent when light colored, dark material nearly opaque; commonly zoned | other = | references = }} Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains the most important source of tin today.

thumb|Crystal structure of cassiterite