Pentagonite

Pentagonite is a rare silicate mineral with formula Ca(VO)Si4O10ยท4(H2O).It was named for the unusual twinning called a fiveling with an apparent five-fold symmetry.Pentagonite was first described in 1973 for an occurrence in Lake Owyhee State Park, Malheur County, Oregon.It occurs as fracture and cavity fillings in tuff and basalt.It occurs with cavansite, heulandite, stilbite, analcime, apophyllite and calcite.
Silicate mineralFormulaIMA symbolStrunz classificationCrystal systemOrthorhombicCrystal classH-M symbolSpace groupCrystal habitTwinningCleavageTenacityMohs scaleLusterDiaphaneitySpecific gravityRefractive indexBirefringencePleochroism2V anglefivelingdimorphcavansiteLake Owyhee State ParkPune districtbasaltheulanditestilbiteanalcimeapophyllitecalciteBibcode