Greenstone (Metabalt)

Hardness: 6-7 (Mohs scale), Color: dull green to grayish-green with pale epidote inclusions, Luster: dull to waxy, Crystal structure: fine-grained, Specific gravity: 2.8-3.0

Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt) under high pressure and low temperature, often in subduction zones. Typically Proterozoic to Paleozoic in age.

Used historically for stone tools (axes), currently used as crushed stone for construction, decorative garden rocks, and occasionally polished for lapidary work.

The green color is primarily due to the presence of chlorite, actinolite, and epidote. It was highly prized by Neolithic cultures for making 'celt' axes due to its toughness.

Identified by its distinctive green hue and lack of foliation compared to other schists. Commonly found in old mountain belts like the Appalachians or the Pacific Northwest. Look for it in riverbeds or glacial tills as rounded cobbles.