idocrase

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idocrase (vesuvianite) A mineral, with the formula Ca10(Mg,Fe)2Al4Si9O34(OH,F)4, closely related to the garnet group; sp. gr. 3.4; hardness 6.5; green; normally massive or granular; occurs in contact-metamorphosed (see THERMAL METAMORPHISM) limestones along with grossular, scapolite, and wollastonite.