Greenstone

Greenstone, general term for dark green, compact metamorphic rocks formed by the alteration of dark-coloured IGNEOUS ROCKS. Basalt, a common example, is a major component of the greenstone belts of the Canadian SHIELD. These belts contain the Shield's principal GOLD and base-metal mines.

Greenstone

Greenstone, general term for dark green, compact metamorphic rocks formed by the alteration of dark-coloured IGNEOUS ROCKS. Basalt, a common example, is a major component of the greenstone belts of the Canadian SHIELD. These belts contain the Shield's principal GOLD and base-metal mines. The term greenstone is also used for green ornamental materials used for sculpture and gems, such as nephrite jade, serpentine, fuchsite (a chrome-mica rock) and chlorastrolite (a tortoiseshell-like GEMSTONE composed of pumpellyite needles).