goldmanite

{{Infobox mineral | name = Goldmanite | image = Goldmanite.jpg | alt = | caption = Goldmanite from Slovakia | category = Nesosilicates, garnet | formula = {{chem2|Ca3(V^{3+},Al,Fe^{3+})2(SiO4)3}} | IMAsymbol = Glm | molweight = | strunz = 9.AD.25 | dana = 51.4.3b.4 | system = Isometric | class = Hexoctahedral (mm) H-M symbol: (4/m 2/m) | symmetry = Iad | unit cell = a = 12.01 Å V = 1,732.32 Å3; Z = 8 | color = Green, brownish–green | colour = | habit = Dodecahedral crystals and anhedral grains | twinning = | cleavage = None | fracture = | tenacity = | mohs = 6–7 | luster = Vitreous | streak = White | diaphaneity = Transparent to sub-opaque | gravity = 3.74 – 3.77 (measured) | density = | polish = | opticalprop = Isotropic, may show weak anisotropism | refractive = n = 1.821 | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = Cr, Mn, Mg | alteration = | other = | prop1 = | prop1text = | references = }} Goldmanite is a green or greenish-brown silicate mineral of the garnet group with a chemical formula of {{chem2|Ca3(V^{3+},Al,Fe^{3+})2(SiO4)3}}.

==Discovery== It was first described in 1964 for an occurrence in the Laguna District, Cibola County, New Mexico and is named after Marcus Isaac Goldman (1881–1965), an American petrologist. The type locality, South Laguna (or Sandy) mine area, was in vanadium rich clay within a metamorphosed uranium-vanadium deposit in sandstone. While studying these deposits, it was noted that garnet in relatively unmineralized sandstone is colorless, whereas garnet in dark well-mineralized rock, containing abundant vanadium clay and uranium deposits was deep green or brownish green. To confirm the green color was due to vanadium, two samples of garnet were separated from dark ore, analyzed, and found to be rich in vanadium. The South Laguna mine area was studied in 1955 and 1956 as part of an investigation of the geology and uranium deposits of the Laguna district by the USGS.