Quartz

Quartz is one of the most common and geologically important minerals on Earth. It is composed of silicon and oxygen with the chemical formula SiO₂ and occurs in an enormous variety of geological environments. Quartz can form as colourless transparent crystals, cloudy or massive material, veins, grains within rocks, drusy coatings and many other crystal habits. Well-formed Quartz crystals are commonly recognised by their six-sided prismatic appearance and pointed terminations, although Quartz belongs to the trigonal crystal system rather than the hexagonal crystal system. Pure Quartz is colourless, but trace elements, structural defects, natural irradiation and mineral inclusions can produce many different colours and varieties. Well-known Quartz varieties include Amethyst, Citrine, Smoky Quartz and Rose Quartz, while included Quartz materials such as Garden Quartz and Hematoid Quartz gain their distinctive appearance from minerals enclosed within or associated with the Quartz. Quartz is also the main crystalline component of many forms of chalcedony and agate, although those materials have a much finer microcrystalline structure. Quartz forms in igneous, metamorphic, sedimentary and hydrothermal environments and is an important component of rocks such as granite, quartzite and sandstone. Its combination of hardness, chemical durability and abundance means Quartz can survive weathering and become concentrated in soils, river sediments and beaches. Quartz has also been used by humans for thousands of years for tools, carvings, jewellery and decorative objects, and its piezoelectric properties later made it important in electronic and timing applications.