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GREENSTONE #1 Greenstone - Other specific examples: #1 | #2 | #3 | #4 
Detail of this specimen
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Composition
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Description
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 rock, although technically it means one with a mafic parent. But without knowing what the parent is there is no definitive way in hand specimen to tell what the parent was. This rock is known to have had a shale parent so technically it is a chlorite schist not a greenstone (which has a mafic parent), but in the field we would just call it a greenstone. Compare with greenschist.What is important with all these rocks, however, is that they have undergone low grade metamorphism (greenschist facies) to produce chlorite crystals with a schistose foliation |
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Tectonic Association
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 (click picture for larger version). The next rock in the sequence is amphibolite.
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Type of Metamorphism
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