Greenstone

Hardness on Mohs scale ranges from 5 to 6; Color is typically dull green, grayish-green, or dark green due to chlorite, epidote, and actinolite; Luster is dull to sub-vitreous; Crystal structure is cryptocrystalline to microcrystalline, massive; Cleavage is generally poor or absent; Specific gravity is roughly 2.8 to 3.0.

Formed through low-grade regional metamorphism of mafic igneous rocks such as basalt, gabbro, or diabase, typically in ancient greenstone belts dating from the Archean and Proterozoic eons.

Used historically by indigenous peoples for making stone axes and tools, sometimes polished for lapidary use and jewelry, and occasionally as crushed aggregate in construction.

Greenstone belts are among the oldest geological formations on Earth, frequently hosting significant deposits of gold, copper, and nickel ores.

Easily identified by its characteristic greenish hue and water-worn pebble shape in glacial outwash or stream beds, commonly found in regions with ancient shields such as the Canadian Shield and Fennoscandia.