missourite

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• Leucite — is a rock forming mineral composed of potassium and aluminium tectosilicate K [AlSi2O6] . Crystals have the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically isotropic, and are therefore… …   Wikipedia

• Ijolite — (derived from the first syllable of the Finnish words Ii vaara, Iijoki, c., common as geographical names in Finland, and the Gr. Xiflos, a stone), is an igneous rock consisting essentially of nepheline and augite. Ijolite is a rare rock type of… …   Wikipedia