Chapter II: Methods for specifying quartz crystal orientation and their determination by optical means

The chemist describes quartz as silicon dioxide, SiO2, crystallized in hard, brittle, glass-like, six sided prisms, often with pyramidal terminations; melting point 1750° Centigrade, density 2.65, hardness on Moh's scale 7. It transforms from alpha to beta quartz at 573°C under atmospheric pressure. Under stress it transforms at lower temperatures. Alpha quartz is insoluble in ordinary acids but soluble in hydrofluoric acid; and in hot alkalis.