Definition
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks
Marl is an unconsolidated sedimentary rock consisting of clay and lime
History
Origin
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Discoverer
Unknown
William Smith
Etymology
From the Middle High German verb gneist (to spark; so called because the rock glitters)
From Old French marle, from Late Latin marglia
Class
Metamorphic Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Soft Rock
Family
Group
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Other Categories
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock