Quartz (Smoky/Milky Pebble)

Physical Properties

Hardness: 7 (Mohs scale), Color: Brownish-grey, Luster: Vitreous to waxy (when water-worn), Crystal structure: Trigonal/Hexagonal, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.65

Formation & Geological History

Formed through crystallization of silica-rich magma or precipitation from hydrothermal fluids. This specimen is a water-worn river pebble, likely millions of years old, shaped by mechanical erosion in a fluvial environment.

Uses & Applications

Raw quartz is used in glassmaking, electronics (piezoelectricity), and as an abrasive. Smooth pebbles are used in landscaping, aquariums, and rock tumbling for hobbyists.

Geological Facts

Quartz is the second most abundant mineral in Earth's continental crust. Smoky quartz gets its color from natural irradiation of aluminum impurities within the crystal lattice.

Field Identification & Locations

Identify by its hardness (scratches glass) and lack of cleavage. It is commonly found in riverbeds, beaches, and glacial deposits worldwide. Collectors look for clarity and internal fractures.

Identified on: 5/15/2026

Mode: Standard