Quartz

Hardness: 7 (Mohs scale), Color: Varies widely, including white, grey, pink, brown, purple, green, yellow, and clear. Often translucent to opaque. Luster: Vitreous (glassy) to waxy. Crystal Structure: Hexagonal (trigonal) crystal system. Often found as prismatic crystals, massive, granular, or cryptocrystalline (as in chalcedony). Cleavage: None. Fracture: Conchoidal. Specific Gravity: 2.65.

Quartz forms under a wide range of temperatures and pressures in igneous, metamorphic, and sedimentary rocks. In igneous rocks, it crystallizes from molten magma or lava. In metamorphic rocks, it forms during regional or contact metamorphism. In sedimentary rocks, it is a common detrital mineral and also forms from chemical precipitation (e.g., chert, flint). Its geological age can vary from Precambrian to recent, depending on the rock formation.

Industry: Crucial for electronics (oscillators, filters), glass manufacturing, abrasives, and as a raw material in ceramics. Jewelry: Many varieties are used as gemstones. Construction: Sand (primarily quartz) is used in concrete and mortar. Used as an aggregate in various building materials.

Quartz is the second most abundant mineral in Earth's continental crust, after feldspar. Many varieties of quartz are semi-precious gemstones, including amethyst, citrine, rose quartz, smoky quartz, and aventurine. The piezoelectric properties of quartz make it essential in electronics for oscillators and filters (quartz crystals).

Field Identification: High hardness (scratches glass), conchoidal fracture, and lack of cleavage are key identifiers. Its glassy luster and often hexagonal crystal habit (when present) are also distinctive. Common Locations: Found globally in almost all types of rocks. Large deposits are found in Brazil, Arkansas (USA), and various parts of Europe and Asia. Tips for Collectors: Look for well-formed crystals in pegmatites and hydrothermal veins, or interesting color varieties in sedimentary and metamorphic environments.