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Greenstone

A metamorphic rock derived from basalt or chemically equivalent rock such as gabbro. Greenstones contain sodium-rich plagioclase feldspar, chlorite, and epidote, as well as quartz. The chlorite and epidote make greenstones green.

Any of various altered basic igneous rocks colored green by chlorite, hornblende, or epidote. A basic igneous rock having a green color due to iron-bearing silicate minerals; quarried and fabricated for structural and decorative dimension stone. Greenstone is a very general term used in geology to describe a great variety of rock types usually formed from.

A nondescript rock, easily confused with greenschist, chlorite schist, or phyllite. All these rocks dominated by chlorite with good cleavage can look similar. The term greenstone is actually a field term applied to any chlorite rich rockderived from a mafic parent. But without knowing what the parent was there is no definitive way in hand specimen to tell what the parent was.

Greenstone belts are so called because of the green hue imparted by the chlorite minerals within the rocks. Greenstone belts are mainly found in Australia, southern Africa, and Canada, and may be found included within igneous and metamorphic rock such as basalt, granite and gneiss.

Greenschist

Greenschist is associated with major mountain building events when mafic igneous rocks (basalts or gabbros) are metamorphosed through depth of burial, and proximity to batholiths. A nondescript rock, easily confused with greenstone, phyllite, and chlorite schist. It has undergone low grade metamorphism (greenschist facies), to produce chlorite crystals with a schistose foliation. Aside from that it is hard to define distinguishing features. In general, the term greenschist applies to any rock that fits this description.

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