metamorphic or igneous

Quartz River Pebble with Algae

Silicon Dioxide (SiO2) with organic biofilm

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Creamy white with green surface organic matter; Luster: Vitreous to waxy; Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture).

Hardness: 7 on Mohs scale
Color: Creamy white with green surface organic matter
Luster: Vitreous to waxy

Identified June 19, 2026More metamorphic or igneous →

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Physical properties

Hardness: 7 on Mohs scale; Color: Creamy white with green surface organic matter; Luster: Vitreous to waxy; Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture).

Formation & geological history

Formed from hydrothermal veins or metamorphic activity, then eroded and smoothed by high-energy water transport (river or beach action) over thousands of years.

Uses & applications

Commonly used in landscaping, decorative ground cover, aquarium gravel, and as a source of industrial silica if found in large deposits.

Geological facts

This specimen appears to be 'green' not due to mineral content, but due to chlorophyta (green algae) growing on its wet surface. Quartz is one of the most chemically resistant minerals on Earth's surface.

Field identification & locations

Field identification involves checking for hardness (won't scratch with a knife) and the rounded 'tumbled' shape. Often found in riverbeds, glacial tills, and shorelines.