Description

Quartz is the second most common mineral in the Earth’s continental crust.  It is mainly composed of Silica or Silica based minerals.  Although Quartz is known by a variety of names, the most important distinction between types of Quartz is that of macro-crystalline, individual crystals visible to the unaided eye, and micro-crystalline, where aggregates of crystals are only visible under high magnification.  There are many forms of Quartz including Chalcedony, Amethyst, Citrine, and Carnelian which are results of mineral impurities or heat treatments.

A member of the evaporite group of minerals and the soft rock comprising anhydrite formed by precipitation of calcium sulfate from evaporation of seawater. Anhydrite can also form through the dehydration of gypsum, another sulfate mineral found in evaporites. Anhydrite may occur as a cap rock above salt domes.