Quartz

Hardness: 7 on Mohs scale. Color: In the image, it appears white to milky-white, possibly with slight green tints from impurities. Can be colorless, purple (amethyst), pink (rose quartz), yellow (citrine), brown/black (smoky quartz), etc. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal) crystal system. Often found as prismatic crystals with striations, or as massivge, granular, or cryptocrystalline aggregates. Cleavage: None, exhibits conchoidal fracture. Specific Gravity: 2.65.

Formation Process: Quartz forms in a wide range of geological environments. It can precipitate from hydrothermal solutions, crystallize from magmas (igneous rocks), form from the recrystallization of sedimentary rocks during metamorphism, or be deposited as clastic grains in sedimentary environments. Geological Age: Extremely common and has been forming throughout Earth's history, from Precambrian to the present day. Environments: Found in igneous rocks (granite, rhyolite), metamorphic rocks (gneiss, schist, quartzite), and sedimentary rocks (sandstone, chert). Large crystals often found in pegmatite veins and hydrothermal veins.

Industry: Used in electronics (oscillators, filters), optics (lenses, prisms), abrasives, and as a component in concrete and mortar. Construction: Crushed quartz sand is a primary ingredient in glass manufacturing and ceramics. Jewelry: Many varieties of quartz (amethyst, citrine, rose quartz, smoky quartz, chalcedony, agate, jasper) are widely used as gemstones and for ornamental carvings. Collecting Value: Well-formed crystals and rare varieties are highly prized by collectors.

Quartz is the second most abundant mineral in Earth's continental crust, after feldspar. It is resistant to weathering, making it a dominant mineral in river and beach sand. The piezoelectric property of quartz allows it to generate an electric charge when subjected to mechanical stress, and vice versa. This property is crucial for its use in watches and electronics. The name 'quartz' comes from the German 'Quarz', which ultimately may have Slavic origins (e.g., Czech 'křemen').

How to Identify in the Field: Look for its characteristic vitreous luster, hardness (it will scratch glass and steel), conchoidal fracture (smooth, curved breaks like broken glass), and lack of cleavage. It is often translucent to opaque. The specimen in the image appears to be a massive form of milky quartz. Common Locations: Found globally. Major sources of crystalline quartz include Brazil, Arkansas (USA), and various parts of the Alps. Sandstone and quartzite are found in many continental regions. Tips for Collectors: Look for clear, well-formed crystals in vugs or veins in igneous and metamorphic rocks. Massive quartz is very common in stream beds and as 'float' in fields due to its resistance to weathering.