Quartz

Hardness: 7 (Mohs scale), Color: Varies widely, often white, colorless, grey, purple (amethyst), yellow (citrine), pink (rose quartz), black (smoky quartz), Luster: Vitreous (glassy), Crystal Structure: Hexagonal (trigonal system), often forming prismatic crystals with pyramidal terminations. Can also be massive, granular, or cryptocrystalline.

Quartz forms in a wide variety of geological environments. It can crystallize from magma and hydrothermal solutions, making it common in igneous and metamorphic rocks. It is also highly resistant to weathering, accumulating in sedimentary deposits like sandstone. Its geological age spans from the earliest Precambrian to present-day formations.

Industry: Electronics (oscillators, filters), optics (lenses, prisms), abrasives (sandpaper, grinding media), glass manufacturing. Construction: A major component of sand and gravel used in concrete, mortar, and asphalt. Jewelry: Many varieties are popular gemstones (amethyst, citrine, rose quartz, smoky quartz, rock crystal).

Quartz is one of the most abundant minerals in the Earth's crust. It is piezoelectric, meaning it generates an electric charge when subjected to mechanical stress, and vice versa. This property makes it valuable in electronics. Amethyst is the most prized variety of quartz, known for its beautiful purple color. Rose quartz is often associated with love and emotional healing.

Field identification: Look for its glassy luster, conchoidal fracture (shell-like breaks), and its hardness (it can scratch glass and steel). It often forms distinct hexagonal crystals. Common locations: Found globally in various rock types including granite, gneiss, schist, quartzite, sandstone, and in veins within many other rocks. Tips for collectors: Look for crystal forms in vugs and geodes, or well-formed crystals in pegmatites. Riverbeds and beaches are good places to find well-rounded quartz pebbles.