VERMICULITE
VERMICULITE Vermiculite – Mg0.7(Mg,Fe,Al)6(Si,Al)8O20(OH)4·8H2O – is a phyllosilicate (mica), a relatively common alteration product. It has a number of very important industrial applications, which are based on the property of vermiculite to expand (“exfoliate”) when heated, which is due to the water contained between the leaves of the mineral. Famous deposits of vermiculite are the […]
VESUVIANITE
VESUVIANITE Vesuvianite – Ca10(Mg, Fe)2Al4(SiO4)5(Si2O7)2(OH,F)4 – is a sorosilicate of more restricted occurrence, typical of impure marbles that have undergone contact metamorphism. It has no economic importance beyond its occasional use as a gemstone. An old name for vesuvianite, still widely used, is “idocrase”. Vesuvianite is part of the Vesuvianite Group and is isostructural with […]
VOLCANIC GLASS
VOLCANIC GLASS Volcanic glass, also called obsidian, is a very common, amorphous material that occurs only in lavas and hypabyssal intrusive rocks (sills and dykes), as a fundamental mass and containing small crystals and phenocrysts. Its formula depends on the type of rock and is complex, very variable. 4. Transmitted Light Microscopy Refraction indices: Not […]
VAESITE
VAESITE Vaesite is a very rare sulfide, occurring in some very specific parageneses. It is not an ore. It is classified in the Pyrite Group. It is isostructural with cattierite, with which it forms a series. It may contain Co and Fe, and there is a variety with Se. Vaesite crystals appear as cubes and […]