SILLIMANITE
SILLIMANITE Sillimanite – Al2SiO5 – is a rarer nesosilicate, typical of medium to high grade metamorphic rocks, used as an industrial mineral in the production of ceramics. It is one of the polymorphs of the Al2SiO5 Group, together with kyanite and andalusite. It is usually very pure; but may contain some Cr and Fe. The […]
STAUROLITE
STAUROLITE Staurolite – (Fe,Mg)2(Al,Fe)9O6[Si4O22](O,OH)2 – is a more or less common nesosilicate that is characteristic of pelitic metamorphic rocks. It is important as an industrial mineral, but economically viable occurrences (in placers) are so rare that the industrial use of staurolite is restricted by the simple lack of ore. Twins are common in staurolite. There […]
SKUTTERUDITE
SKUTTERUDITE Skutterudite – (Co,Fe,Ni)As2-3 – is a rarer arsenate. It is a Co ore, usually also a Ni ore, with As as a by-product. It is rarely the main ore mineral, it is usually an accessory mineral in complex mineral assemblages. It is classified in the Perovskite Group, Skutterudite Subgroup. There are always varying amounts […]
SILVER
SILVER Silver – Ag – is a rarer native element, very important as a silver ore. The metal has a multitude of uses and a huge and growing number of industrial applications. Dendritic silver pieces are worth much more in the collector minerals market than their weight in metal. Silver is classified in the Copper […]
SERPENTINE
SERPENTINE Serpentine – Mg3Si2O5(OH)4 – is a very common phyllosilicate, occurring mainly in metamorphic rocks. It is a component of rocks with varied applications, such as soapstone (steatite) and agalmatolite. “Serpentine” is actually not a mineral, but just a generic term used for minerals in the Kaolinite-Serpentine Group. The Group is composed of: Clinochrysotile – […]
SCHEELITE
SCHEELITE Scheelite – Ca(WO4) – is a restricted occurrence tungstate. It is, after wolframite, the second most important ore of tungsten, a strategic metal. Well-formed crystals are rare and fetch high prices among collectors. When devoid of inclusions, it can be used as a gem. Scheelite can be synthesized in laboratory (Czochralski process) and has […]
SANIDINE
SANIDINE Sanidine – (K,Na)(Si,Al)4O8 – is a common tectosilicate, a high-temperature potassium feldspar typical of volcanic and hypabyssal rocks. Only the rare colored varieties have any economic importance. High-temperature sanidine (“high sanidine”) is stable at temperatures above 800°C and low-temperature sanidine (“low sanidine”) is stable between 650 and 800°C. Below 650ºC, orthoclase and microcline are […]