
Quartz Value, Price, and Jewelry Information ...
Quartz is an unusual mineral. It is stable below 573 degrees Centigrade, but between 573 and 870 degrees, tridymite, (another silica mineral,) forms. At 1470 degrees, tridymite undergoes a structural rearrangement and becomes cristobalite, which is isometric. At 1710 degrees, cristobalite melts to a viscous liquid.