Definition
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Etymology
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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
From the Middle High German verb gneist (to spark; so called because the rock glitters)
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Pantellerite is a peralkaline rhyolite. It has a higher iron and lower aluminium composition than comendite
From Pantelleria, a volcanic island in the Strait of Sicily
Fine Grained Rock, Opaque Rock