Composition
Chlorite
Epidonte
Actinolite
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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 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. This rock is known to have had a mafic parent so technically it is 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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