Quartz

Hardness: 7 (Mohs scale); Color: Transparent to translucent, often white, gray, clear, or milky (as seen here, possibly milky quartz), but can come in various colors due to impurities; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (fractures conchoidally); Specific Gravity: 2.65

Quartz is one of the most abundant minerals in the Earth's crust. It forms in a wide range of geological environments and temperatures. It can crystallize from magma (igneous rocks), precipitate from hydrothermal veins, or form during metamorphic processes. It is also a major component of many sedimentary rocks derived from igneous and metamorphic sources. Its abundance means it is found in rocks of all geological ages, from Precambrian to Cenozoic.

Quartz has numerous uses: in industry (e.g., electronic oscillators, abrasives, glassmaking, foundry sand), construction (e.g., aggregate for concrete, building stone), and jewelry (especially its gemstone varieties like amethyst, citrine, rose quartz, and smoky quartz).

Quartz is the second most abundant mineral in the Earth's continental crust, second only to feldspar. Its excellent hardness and resistance to weathering make it a dominant constituent of sand and soils. Large, well-formed crystals are highly sought after by collectors.

In the field, quartz can be identified by its relative hardness (scratches glass readily), its glassy luster, conchoidal fracture (smooth, curved breaks), and lack of cleavage. Milky quartz, as potentially seen here, is very common and identified by its cloudy white appearance. It is found globally in almost every type of rock, from granites and gneisses to sandstones and quartzites. When encountered in veins, as shown, it often indicates hydrothermal activity.