Definition
Variolites are a group of dark green basic igneous rocks which exhibit pale colored spots, or spherules, especially on weathered surfaces, that give them a pockmarked appearance
Greywacke is defined as a dark coarse-grained sandstone rock which contains more than 15 per cent clay
History
Origin
France
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Discoverer
Unknown
Unknown
Etymology
From Latin varius, speckled, variegated
From German Grauwacke, from grau grey + wacke
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Family
Group
Volcanic
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Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock