Quartz Pebble (Chalcedony/Agate variety)

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, beige, translucent milky white; Luster: Waxy to vitreous; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & Geological History

Formed through the precipitation of silica from groundwater in cavities of other rocks or as water-worn debris in sedimentary environments. Common in all geological eras, often found in alluvial deposits.

Uses & Applications

Used in jewelry (tumbled stones), industrial abrasives, glass making, and as decorative landscaping gravel.

Geological Facts

Quartz is the second most abundant mineral in Earth's continental crust. This specific specimen appears to be a water-worn river pebble, naturally polished by the action of water and sand over time.

Field Identification & Locations

Identify in the field by its hardness (will scratch glass), lack of cleavage, and translucent 'glow' when held to a light. Extremely common in riverbeds and beaches worldwide.

Identified on: 4/19/2026

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