Clear Quartz (or Rock Crystal)

Hardness: 7 (Mohs scale); Color: Colorless and transparent (as seen in the image), but can also be milky white, cloudy, or inclusions can add colors; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (fractures conchoidally); Specific Gravity: 2.65

Quartz forms under a wide range of temperatures and pressures from igneous, metamorphic, and sedimentary processes. It is generally very old, forming over geological timescales (millions to billions of years) as magma cools, through hydrothermal activity, or through the weathering and redeposition of older rocks.

Industry: Electronics (oscillators, filters, frequency control), optics, abrasives, glassmaking, ceramics. Jewelry: Widely used as gemstones, often faceted into beads, cabochons, or carved into ornate designs. Construction: A major component of many building materials like concrete, mortar, and sandpaper. Collecting Value: Well-formed crystals are highly sought after by collectors.

Quartz is the second most abundant mineral in Earth's continental crust, after feldspar. Its piezoelectric properties (generating electric charge under mechanical stress) make it vital in electronics. Varieties include amethyst, citrine, smoky quartz, rose quartz, and agate. The beads in the image are faceted, meaning they have been cut and polished to create multiple flat surfaces (facets) to enhance their sparkle.

In the field, clear quartz can be identified by its hardness (scratches glass), glass-like luster, and often hexagonal crystal habit (though individual crystals might not be visible in rough form). Its conchoidal fracture (shell-like breaks) is also distinctive. It is commonly found in igneous rocks (granite, pegmatite), metamorphic rocks (gneiss, schist, quartzite), and sedimentary rocks (sandstone, chert). Large crystal deposits are found worldwide, notably in Brazil, Arkansas (USA), and the Alps.