Quartz

Hardness: 6-7 (Mohs scale), Color: Variable, often red, pink, white, gray, brown, green, black. Luster: Vitreous to greasy. Crystal Structure: Trigonal. Cleavage: None. Specific Gravity: 2.65

Quartz forms through the crystallization of silica (SiO2) from hydrothermal solutions, igneous melts, or during metamorphic processes. It is a primary constituent of granites and other felsic igneous rocks, and is also found in sedimentary rocks (like sandstone) and metamorphic rocks (like quartzite). Its formation can span billions of years, depending on the geological context.

Quartz is widely used in many industries. It is a key component in glass manufacturing, abrasives, and as a raw material for silicon production. Due to its piezoelectric properties, it is used in electronic devices like watches, radios, and computers. Attractive varieties of quartz are extensively used as gemstones and in jewelry. In construction, it's a common aggregate in concrete and asphalt.

Quartz is one of the most abundant minerals in Earth's crust. It forms in a variety of temperatures and pressures, making it present in almost all rock types. Many varieties of quartz exist, distinguished by their color, structure, or impurities, such as Amethyst, Citrine, Rose Quartz, Smoky Quartz, and Chalcedony.

In the field, quartz can be identified by its glassy luster, hardness (it can scratch glass and steel), and lack of cleavage (it fractures conchoidally). It is ubiquitous and can be found globally in various geological settings, including igneous, metamorphic, and sedimentary terrains. For collectors, looking for well-formed crystals in vugs or veins, or colorful varieties in weathered rock, can be rewarding. Its resistance to weathering means it is often found as pebbles and sand in rivers and beaches.