sedimentary or metamorphic

Greenstone / Chert

Cryptocrystalline Quartz (SiO2) or Altered Basalt

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 →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.

Other sedimentary or metamorphic specimens

See all

Shale or Argillite

Shale (sedimentary) / Argillite (metamorphic)

Sedimentary or Metamorphic (low-grade)

Anthracite Coal

Anthracite (Carbon-rich Sedimentary-to-Metamorphic Rock)

metamorphic

Milky Quartz with Iron Inclusions

Quartz (Silicon Dioxide, SiO2)

mineral

Anthracite Coal

Anthracite (Carbon-based sedimentary-derived metamorphic rock)

metamorphic

Jasper Conglomerate (Puddingstone)

Siliceous Conglomerate (Quartz and Jasper clasts in a fine-grained matrix)

sedimentary

River Pebbles and Quartz

Mixed Igneous, Sedimentary, and Metamorphic Rocks (Silicon Dioxide SiO2 dominant)

mixed