GeologyRocks

Silica Tetrahedra

All silicate minerals have a structure based on the silica tetrahedra, an arrangement of 1 silica atom and 4 oxygen atoms. The chemical formula for this is SiO₄.

Silicate

A mineral formed from silica and oxygen. The majority of rock forming minerals are silicates. Examples are quartz and pyroxene.

Silliminite

A polymorph whose other two minerals are kyanite and andalusite.

Skarns

Limestone or marble permeated by hot magma can sometimes create deposits: 'skarns'. Silicon and iron in the magma combine with calcium and magnesium in the limestone to form silicate minerals such as wollastonite. Also, hydrothermal solutions can leave ore minerals such as tungten, iron and zinc. 

Zeolite

A group of hydrous alumino silicates, which are characterized by their easy and reversible loss of water. There are 48 known naturally occurring zeolites. They are used in a variety of industries, including cat litter.

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Zoned Crystal

A crystal with concentric layers differing in chemical composition representing a complex crystallisation history.