Definition
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Ijolite is an intrusive igneous rock which is composed mainly of nepheline and an alkali pyroxene, usually aegirine-augite
From the first syllable of the Finnish words Ii-vaara, Iijoki, &c. commonly used geographical names in Finland, and the Gr. Xiflos, a stone
Durable Rock, Medium Hardness Rock
Coarse Grained Rock, Opaque Rock
Rhyolite is a fine-grained igneous rock which is rich in silica
From German Rhyolit, from Greek rhuax lava stream + lithos stone
Coarse Grained Rock, Opaque Rock