Quartz (River Pebble)

Physical Properties

Hardness: 7 on Mohs scale; Color: Milky white to tan with iron staining (reddish-brown); Luster: Vitreous to waxy when weathered; Crystal Structure: Trigonal (hexagonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & Geological History

Formed through crystallization of silica-rich hydrothermal fluids or within igneous pegmatites. This specific specimen has been rounded into a 'river cobble' by mechanical weathering and water erosion over thousands of years.

Uses & Applications

Common industrial uses include glass making, abrasives, and hydraulic fracturing proppant. In rounded pebble form, it is used for landscaping, garden decor, and aquarium substrates.

Geological Facts

Quartz is one of the most abundant minerals in Earth\'s crust. It is highly resistant to both chemical and physical weathering, which is why it often remains as rounded pebbles long after other minerals have broken down.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass and steel) and lack of cleavage. It is commonly found in riverbeds, glacial deposits, and beaches. Collectors should look for internal fractures or clarity, though this specimen is opaque 'bull quartz'.

Identified on: 4/21/2026

Mode: Standard