Quartz

Hardness: 7 on Mohs scale; Color: Variable, often white, colorless, clear, brown, but can be pink, purple, yellow, or smoky; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Quartz forms in a wide range of geological environments. It crystallizes from magma in igneous rocks, precipitates from hydrothermal solutions in veins, and is a major component of sandstones and quartzites formed from erosion and deposition of pre-existing rocks. Its formation can span billions of years, from early Earth to present processes.

Industry: Manufacturing of glass, ceramics, electronics (oscillators, filters), abrasives, and refractory materials. Jewelry: Precious and semi-precious gemstones (e.g., amethyst, citrine, clear quartz). Construction: Component in concrete, mortar, and as a decorative aggregate. Collecting: Highly sought after by mineral collectors for its crystal habit and aesthetic variations.

Quartz is one of the most abundant minerals in the Earth's crust. It is a key component of many rocks (igneous, metamorphic, and sedimentary). Varieties like amethyst, citrine, smoky quartz, and rose quartz are popular gemstones. Pure quartz crystals often form striking hexagonal prisms.

In the field, quartz can be identified by its relative hardness (scratches glass), glass-like luster, and lack of cleavage (it will break with a conchoidal or shell-like fracture rather than along flat planes). Its common occurrence in veins and as a primary mineral in many rock types makes it widespread. It's often found in igneous rocks like granite, metamorphic rocks like gneiss and schist, and sedimentary rocks like sandstone. To confirm, a scratch test against a steel file or glass can be performed, as quartz will scratch both.