sedimentary or metamorphic

Greenstone / Chert

Cryptocrystalline Quartz (SiO2) or Altered Basalt

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Sage green with tan/yellow veins; Luster: Dull to waxy; Structure: Microcrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Hardness: 6
Color: Sage green with tan/yellow veins
Luster: Dull to waxy

Identified February 20, 2026More sedimentary or metamorphic →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Sage green with tan/yellow veins; Luster: Dull to waxy; Structure: Microcrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Formation & geological history

Formed either as a sedimentary deposit of silica-rich organic remains (chert) or through low-grade metamorphism of mafic igneous rocks (greenstone). Often found in riverbeds or coastal regions as water-worn pebbles.

Uses & applications

Commonly used for lapidary work, cabochons, and decorative landscaping. Historically used for stone tools due to sharp fracture edges.

Geological facts

The green color is typically caused by chlorite or epidote inclusions. Specimens like this one exemplify how tectonic movement creates internal fractures that later fill with secondary minerals, creating beautiful veining pattern.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and waxy texture. Frequently found in the Franciscan Assemblage of California or glacial till in the Midwest. Collectors look for unique banding or 'picture' patterns.