STILPNOMELANE
STILPNOMELANE Stilpnomelane – (K,Ca,Na)(Fe,Mg,Al)8(Si,Al)12(O,OH)36·nH2O – is a rarer phyllosilicate. It does not constitute ore. It is classified in the Stilpnomelane Group and is isostructural with franklinphilite, parsettensite and chalcodite. It has three varieties. Under the microscope, the optical properties vary depending on varying degrees of the Fe oxidation state; distinguishes between ferro-stilpnomelan and ferri-stilpnomelan. Macroscopically […]
SULPHUR
SULPHUR Sulphur – S8 – is a relatively common native element, characteristic of various geological environments. The mineral is written “sulphur”; the commodity is written “sulfur”. Sulphur is an important mineral, as sulfur has many industrial applications. Sulphur is classified in the Sulphur Group and is a polymorph of rosickyite (monoclinic S, very rare) and […]
SCAPOLITE
SCAPOLITE Scapolite – (Na,Ca,K)4Al3-6Si9-6O24(Cl,CO3,SO4) – is a rarer tectosilicate, characteristic of some specific geological situations. It is unimportant as an ore, but some varieties are used as gemstones. “Scapolite” is not a mineral, but a generic term referring to the members that make up the series between marialite (of Na) and meionite (of Ca), classified […]
SODALITE
SODALITE Sodalite – Na8Al6Si6O24Cl2 – is a feldspathoid, a tectosilicate of more restricted occurrence, occurring in rocks undersaturated in silica. When blue, it constitutes rocks of high commercial value, such as “Granito Azul Bahia” (which is not granite, of course). It is classified in the Sodalite Group. May contain K, Ca, Fe, Mn, Br, S […]
SPODUMENE
SPODUMENE Spodumene – LiAlSi2O6 – is a rare inosilicate, characteristic of lithium-bearing pegmatites. It is the main mineral in hard rock Li ores. Lithium can be mined in brines or hard rock mines, which are mines located in pegmatites exploiting spodumene, lepidolite, petalite, and other minerals containing Li. Spodumene is classified in the Pyroxene Group, […]
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 – […]