Definition
Gritstone or grit is a hard, coarse-grained, siliceous sandstone
Troctolite is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene. It is an olivine-rich anorthosite, or a pyroxene-depleted relative of gabbro
History
Origin
Pennines, England
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Discoverer
J.J. Ferber
Christian Leopold von Buch
Etymology
From Grit + Stone
From German Troklotit, from Greek trōktēs, a marine fish (taken to be trout)
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Family
Group
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Plutonic
Other Categories
Coarse Grained Rock, Opaque Rock
Coarse Grained Rock, Opaque Rock