Vesuvian

vesuvian [və′sü·vē·ən]

(mineralogy)

leucite vesuvianite

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Vesuvian 

(named for its presence on Vesuvius), or idocrase, a mineral, a natural complex silicate containing in its structure isolated tetrahedrons of Si0₄ and paired groups of Si₂O₇. The following varieties are distinguished: chrome vesuvian (up to 4.3 percent Cr₂O₃), beryllium vesuvian (up to 9.20 percent BeO), cerium vesuvian (up to 16.7 percent Ce₂O₃), and vesuvian containing boron (up to 4.14 percent B₂O₃). It crystallizes in a tetragonal system. It forms crystals of prismatic or bipyramidal form and granular, compact masses. The color is light yellow-green, brownish-green, bright green, or dark brown to black, depending on the composition and admixtures. Its hardness on the mineralogical scale is 6.5; the density is 3,350-3,450 kg/m³. It is formed with limestones and dolomites at the junctures of plutonic magmatic rocks. The minerals usually associated with vesu-vian are garnet, chlorites, epidote, magnetite, and calcite.