One of the most abundant minerals in the earth’s crust. Has a chemical composition of SiO2 and a hardness of seven. One of the index minerals in Moh’s Hardness Scale. Occurs in sedimentary, metamorphic and igneous rocks. Quartz is a very widespread mineral which occurs as an important constituent of igneous rocks which have an excess of silica. Very resistant to mechanical and chemical attack. Massive, fine grained types are called jasper, chert, flint, agate. Coarse crystalline types called amethyst, rose quartz etc.It has the formulae SiO2 and a relative hardness of 7. During the Second World War attempts were made to synthesise quartz, and in 1947 the first optical grade crystals large enough for scientific use were grown by the hydrothermal method.
Related terms: