Greenschist (Greenstone River Pebble)

Physical Properties

Hardness: 3.5-4.5 on Mohs scale; Color: Grayish-green to dull olive; Luster: Pearly to dull; Structure: Foliated with fine-grained texture; Cleavage: Good in one direction but obscured in rounded pebbles; Specific Gravity: 2.8-3.0.

Formation & Geological History

Formed through regional metamorphism of mafic igneous rocks (like basalt) at low temperatures and high pressures. This specific specimen has been further shaped by fluvial (river) erosion, resulting in its smooth, rounded 'water-worn' shape.

Uses & Applications

Used primarily for landscaping, decorative gravel, and occasionally as a low-grade carving stone. Historically, hard varieties were used for stone tools.

Geological Facts

The green color is primarily due to the presence of minerals like chlorite, epidote, and actinolite. It represents a specific 'facies' (set of conditions) in metamorphic geology.

Field Identification & Locations

Identify by its distinct greenish tint and fine-grained, slightly layered texture. It is often found in riverbeds near mountainous metamorphic belts. Collectors should look for signs of 'schistosity' or subtle alignment of mineral grains.

Identified on: 4/21/2026

Mode: Standard