Definition
Origin
Discoverer
Etymology
Class
Sub-Class
Group
Other Categories
Greywacke is defined as a dark coarse-grained sandstone rock which contains more than 15 per cent clay
From German Grauwacke, from grau grey + wacke
Fine Grained Rock, Opaque Rock
Rapakivi Granite is a hornblende-biotite Granite containing large rounded crystals of orthoclase which are mantled with oligoclase
From Finnish Rapakivi which stands for crumbly rock
Coarse Grained Rock, Opaque Rock