Definition
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Discoverer
Etymology
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Luxullianite is a rare type of granite, known for presence of clusters of radially arranged acicular tourmaline crystals which are enclosed by phenocrysts of orthoclase and quartz in a matrix of quartz, tourmaline, alkali feldspar, brown mica.
From the village of Luxulyan in Cornwall, England, where this variety of granite is found
Coarse Grained Rock, Opaque 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
From the English mud and stone, from low German mudde and stainaz
Fine Grained Rock, Opaque Rock