Definition
Essexite which is also known as nepheline monzogabbro, is a dark gray or black holocrystalline plutonic Iigneous Rock
Mudstone is a fine-grained, dark gray sedimentary rock, which is formed from silt and clay and is similar to shale but has less laminations
History
Origin
USA
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Discoverer
Unknown
William Smith
Etymology
From the locality in Essex County, Massachusetts,US
From the English mud and stone, from low German mudde and stainaz
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Soft Rock
Family
Group
Plutonic
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Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock