parthéite

{{Infobox mineral | name = Partheite | category = Tectosilicate minerals | group = Zeolite group | boxwidth = | boxbgcolor = | image =Parthéite.jpg | imagesize = | caption = | formula = Ca2Al4Si4O15(OH)2·4H2O | IMAsymbol = Pth | molweight = | strunz = 9.GB.35 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c | color = White, colorless | habit = Fibrous, radial | twinning = | cleavage = {100} and {110} | fracture = | mohs = 4 | luster = vitreous | refractive = nα = 1.547 – 1.550 nβ = 1.549 – 1.552 nγ = 1.559 – 1.565 | opticalprop = Biaxial (+) | birefringence = δ = 0.012 – 0.015 | pleochroism = | streak = white | gravity = 2.39 – 2.45 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = | other = | references = }}

Partheite or parthéite is a calcium aluminium silicate and a member of the zeolite group of minerals, a group of silicates with large open channels throughout the crystal structure, which allow passage of liquids and gasses through the mineral. It was first discovered in 1979 in rodingitic dikes in an ophiolite zone of the Taurus Mountains in southwest Turkey. The second discovery occurred in gabbro-pegmatites in the Ural Mountains, Russia. Since its discovery and naming, the chemical formula for partheite has been revised from CaAl2Si2O8·2H2O to include not only water but hydroxyl groups as well. The framework of the mineral is interrupted due to these hydroxyl groups attaching themselves to aluminum centered oxygen tetrahedra. This type of interrupted framework is known in only one other zeolite, the mineral roggianite. As a silicate based mineral with the properties of a zeolite, partheite was first described as zeolite-like in 1984 and listed as a zeolite in 1985. Partheite and lawsonite are polymorphs. Associated minerals include prehnite, thomsonite, augite, chlorite and tremolite.