Quartz

Hardness: 7 on Mohs scale. Color: Appears translucent white/grey in the image, but can be colorless, white, purple (amethyst), pink (rose quartz), brown (smoky quartz), black (morion), or yellow (citrine). Luster: Vitreous (glassy) to waxy. Crystal Structure: Hexagonal (trigonal system). Cleavage: None, exhibits conchoidal fracture. Specific Gravity: 2.65.

Quartz forms in a wide range of geological environments. It can crystallize from magma (igneous rocks like granite and rhyolite), precipitate from hydrothermal solutions in veins, form during regional or contact metamorphism (metamorphic rocks like quartzite and gneiss), and precipitate from low-temperature solutions filling fractures and vugs. It is also a major constituent of clastic sedimentary rocks (like sandstone) due to its resistance to weathering. Geological Age: Varies widely, from Precambrian to Cenozoic, depending on the specific formation.

Industry: Used in electronics (oscillators, filters), optics (lenses, prisms), abrasives, glass manufacturing, and as a component in ceramics. Construction: A primary component of sand and gravel used in concrete, asphalt, and pathways. Jewelry: Many varieties of quartz (e.g., amethyst, citrine, rose quartz, smoky quartz, clear quartz) are widely used as gemstones. Collectors: Valued for well-formed crystals, unique colors, or interesting inclusions. Sculpting: Larger pieces can be used for carving.

Quartz is one of the most common minerals on 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 is one of the most popular and valuable varieties of quartz.

Field Identification: Look for its hardness (it scratches glass), conchoidal fracture, glassy luster, and the common presence of hexagonal crystal forms (though this piece appears anhedral/massive). It does not react with acid. Common Locations: Found globally in almost all rock types. Large deposits occur in Brazil, the Alps, the Himalayas, the USA (Arkansas, New York), and many other countries. Tips for Collectors: Quartz is abundant, but clear, well-formed crystals or rare color varieties are highly sought after. Check for clarity, color saturation (in colored varieties), and the presence of any interesting inclusions or phantoms.