Quartz River Cobble

Physical Properties

Hardness: 7 on Mohs scale; Color: Off-white/Milky; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline in this form); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & Geological History

Formed from hydrothermal veins or as a constituent in igneous/metamorphic rocks. This specific specimen has been shaped and smoothed by fluvial (river) erosion over thousands of years.

Uses & Applications

Used conceptually in landscaping, as a source of high-purity silica for glassmaking, or as a decorative 'worry stone' or paperweight.

Geological Facts

Quartz is the second most abundant mineral in Earth's continental crust. This specimen is an example of 'massive quartz' rather than a distinct crystal point.

Field Identification & Locations

Identify in the field by its inability to be scratched by a steel knife (H=7). Look for the rounded, 'river-worn' texture and waxy surface on white or tan specimens.

Identified on: 4/13/2026

Mode: Standard