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Lamprophyre is uncommon igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions
From Greek lampros bright and shining + porphureos purple
Durable Rock, Medium Hardness Rock
Coarse Grained Rock, Fine Grained Rock, Opaque Rock
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
Durable Rock, Medium Hardness Rock