Quartz

Hardness: 7 on the Mohs scale. Color: Often colorless, white, milky, or gray; can be a wide range of colors due to impurities. Luster: Vitreous (glassy) to greasy. Crystal Structure: Hexagonal (rhombohedral). Cleavage: None (fractures conchoidally). Specific Gravity: 2.65.

Quartz typically forms from the slow crystallization of silica-rich solutions in igneous rocks (e.g., granite, pegmatite), metamorphic rocks (e.g., gneiss, schist, quartzite), and hydrothermal veins. It also precipitates from groundwater in sedimentary environments. Its geological age varies widely depending on the specific rock formation it's found within, ranging from Precambrian to recent deposits.

Industry: Used in glass manufacturing, abrasives, foundry sands, and as a raw material for silicon production. Electronics: Crucial for oscillators, resonators, and filters due to its piezoelectric properties (quartz crystals). Construction: A major component of concrete and mortar (as sand and gravel). Jewelry: Many varieties (e.g., amethyst, citrine, rose quartz) are highly prized as gemstones. Collecting: Valued by mineral collectors for its diverse forms, colors, and crystal habits.

Quartz is one of the most common minerals in Earth's crust, found in a wide variety of igneous, metamorphic, and sedimentary rocks. It is piezoelectric, meaning it can generate an electric charge when subjected to mechanical stress, and vice versa. This property makes it valuable in electronics. Amethyst, citrine, rose quartz, and smoky quartz are all varieties of quartz, distinguished by their color due to different trace impurities or irradiation.

In the field, quartz can be identified by its glassy luster, hardness (it can scratch glass and steel), lack of cleavage, and conchoidal fracture. It often forms well-defined hexagonal prisms with pyramidal terminations. It is commonly found worldwide in virtually all geological environments. For collectors, look for well-formed crystals in pegmatites, hydrothermal veins, and geodes. Transparent and facetable varieties are particularly sought after.