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.
Pyrite is one of the more common inclusions in quartz. It’s an iron sulphide (FeS2) and occurs in an opaque yellow to brownish-yellow colored mineral with a metallic luster.