Minerals and Metals in Ancient India v2.c43.s3.t7.1

v2.c43.s3.t7.1

Quartz is pure silica, SiO₂, and has hardness seven in the Moh’s scale; it represents the headship of a family of a very large number of minerals occurring in the earth’s crust. Silica occurs in nature either as crystalline quartz in unhydrated form, or as chalcedony sub-group of minerals (hardness 6-1/2) which is hydrated silica SiO₂, nH₂O. In pure forms both these materials are colourless, but trace quantities of specific oxides render specific colours and gem-like qualities to them.