3.6" Anatase Crystals, Quartz and Adularia Association - Norway
This incredible specimen contains an association of 5+ metallic, twinned anatase crystals, quartz crystals and adularia (variety of orthoclase). The crystals formed from a schist matrix that was collected from Hardangervidda, Norway. The largest anatase crystal on this specimen measures in at .2" long.
Anatase is composed of titanium dioxide, and typically forms dipyramidal crystals, although variations can occur with mineral clumping. Four pointed X-shaped anatase crystals, while rare, have been found and are known as "X-shaped penetration twins". Horizontal striations can be seen across most anatase mineral faces, with most crystals ending in points, or with variations of flattening on each end.
Adularia is a variety of feldspar that had the chemical formula KAlSi3O8. It's found most often as colorless to white aggregations within metamorphic rock, with one example being formation within cavities of crystalline schists. The crystals are commonly twinned, glassy and prismatic in structure, and in some cases they display opalescent characteristics. Adularia is very similar to orthoclase, even baring the same chemical formula, however it has a different crystalline structure and reacts differently to various tests.
Silicon Dioxide, also know as SiO2 or Quartz, is the second most abundant mineral in the Earth's crust. Quartz crystals generally grow in silica-rich, hot watery solutions called hydrothermal environments, at temperatures between 100°C and 450°C, and usually under very high pressure. Quartz veins are formed when open fissures are filled with hot water during the closing stages of mountains forming, and can be hundreds of millions of years old.