quartz
Instance URI: http://resource.geosciml.org/classifier/cgi/commodity-code/quartz
Within scheme: South Australian Commodity Codes
Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz, several of which are semi-precious gemstones.