Rock Name Grade Grain Size Parent Rock
Fine Grained
Shale or Mudstone
Shale

Medium to
Coarse Grained

Shale, basaltic rocks
Shale, Granite, Andesite
Basalt, Gabbro
Fine Grained
Any rock type
Peat, Lignite, or Bituminous Coal
Basalt, Gabbro, or Peridotite
Fine to
Coarse Grained
Limestone, Dolostone
Quartz Sandstone
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