2.3" Quartz Crystals and Adularia - Hardangervidda, Norway

About Quartz

Quartz is the name given to silicon dioxide (SiO2) and is the second most abundant mineral in the Earth's crust. Quartz crystals generally grow in silica-rich environments--usually igneous rocks or hydrothermal environments like geothermal waters--at temperatures between 100°C and 450°C, and usually under very high pressure. In either case, crystals will precipitate as temperatures cool, just as ice gradually forms when water freezes. Quartz veins are formed when open fissures are filled with hot water during the closing stages of mountain formation: these veins can be hundreds of millions of years old.

Adularia is a variety of feldspar that had the chemical formula KAlSi3O8. It is found most often as colorless to white aggregations within metamorphic rock, usually within cavities of crystalline schists. Adularia crystals are commonly twinned, glassy and prismatic in structure, and in some cases they display opalescent characteristics. Adularia is very similar to orthoclase, even bearing the same chemical formula, but it has a different crystalline structure and reacts differently to various tests. Its name comes from its type locality: the Adula Massif in the Alps of south-central Switzerland.