Clear Quartz (Rock Crystal)

Hardness: 7 on the Mohs scale. Color: Colorless (clear, as seen). Luster: Vitreous (glassy). Crystal Structure: Hexagonal. Cleavage: None. Specific Gravity: 2.65.

Clear quartz forms in a wide variety of geological environments, primarily from the crystallization of silica-rich magmas or hydrothermal solutions. It can also form through metamorphic processes. Its geological age varies widely, from Precambrian to present-day, depending on the specific formation event.

Industry: Used in electronics (oscillators, filters, frequency control), optics (lenses, prisms), and abrasives. Jewelry: Faceted and polished into beads, pendants, and other adornments due to its clarity and durability. Construction: A major component of sand and sandstone used in concrete and building materials.

Quartz is the most abundant mineral in the Earth's crust. Varieties of quartz include amethyst, citrine, rose quartz, and smoky quartz, all owing their different colors to impurities or structural defects. Clear quartz is often referred to as 'rock crystal' and has been highly valued throughout history for its beauty and perceived mystical properties.

To identify clear quartz in the field, look for its characteristic clarity, glassy luster, and typical hexagonal crystal habit (though many pieces are fractured or tumbled). It is harder than common glass and cannot be scratched by a steel knife. It is commonly found in igneous rocks (granites, pegmatites), metamorphic rocks (gneiss, schist, quartzite), and sedimentary rocks (sandstone, chert). Major sources include Brazil, the United States (Arkansas, New York), and the Alps.