The Probert Encyclopaedia of Rocks & Minerals

QUARTZ

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.
Research Quartz