Definition
Greywacke is defined as a dark coarse-grained sandstone rock which contains more than 15 per cent clay
Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock
History
Origin
-
Germany
Discoverer
Unknown
Van Tooren
Etymology
From German Grauwacke, from grau grey + wacke
From Greek tephra, ashes from Indo-European base, to burn
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Family
Group
-
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock