Quartz (Milky/Chalcedony variety)

Physical Properties

Hardness: 7 (Mohs scale), Color: Translucent white to milky grey, Luster: Vitreous to waxy, Crystal structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & Geological History

Formed from silica-rich hydrothermal fluids cooling in cavities or veins within igneous, metamorphic, or sedimentary rocks. It is found in geological settings ranging from Precambrian eras to modern hydrothermal deposits.

Uses & Applications

Industrial use as a source of silicon and glass, microelectronics, watchmaking (piezoelectric properties), and as decorative gravel or tumbled stones for hobbyists.

Geological Facts

Quartz is the second most abundant mineral in Earth's continental crust. It is highly resistant to chemical and physical weathering, which is why it often survives as sand on beaches and riverbeds.

Field Identification & Locations

Identify in the field by its hardness (will scratch glass and steel), lack of cleavage, and conchoidal (glass-like) fracture. Found globally in almost all geological environments, especially in gravel pits and mountain veins.

Identified on: 4/16/2026

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