Hiärneite, a new, Zr-Sb oxide mineral isostructural with calzirtite, from Långban, Sweden
European Journal of Mineralogy Volume 9 Number 4 (1997), p. 843 - 848
published: Jul 23, 1997
manuscript accepted: Jan 31, 1997
manuscript received: Sep 27, 1996
ArtNo. ESP147050904015, Price: 29.00 €
Abstract Hiärneite is a new Sb-bearing mineral isostructural with calzirtite. It occurs in a skarn mineral assemblage, coexisting with phlogopite, calcite, arsenatian fluorapatite, svabite, jacobsite, magnetoplumbite, titanian bindheimite and pyrophanite, from the Lángban deposit, Filipstad, Sweden. The crystals (<200 μm) are strongly coloured in red and include abundant mica grains. They are optically uniaxial (+) and weakly dichroic in shades of orange. Refractive indices calculated from reflectance data are ω = 2.12(2) and ɛ' = 2.16(2) at 589 nm. The average composition, expressed as a calzirtite-type formula (9 cations, 16 oxygens, and Mn2+/Mn3+ calculated to balance charge), is Na0.17Ca1.57Mn2+0.62 Zr4.19 Hf0.02Sb5+1.37Ti0.59Mn3+0.36Mg0.02Fe0..09- O16; a general formula could be written as (Ca, Na, Mn2+)2(Zr, Mn3+)5(Sb, Ti, Fe)2O16- Cell dimensions, obtained from single-crystal diffractometer data indexed on a tetragonal I41/acd cell, are: a = 15.264(1), c = 10.089(2) Å and V = 2350.5(5) Å3 for Z = 8. The strongest powder diffraction lines are [d in k(hkl)(I/I0): 3.45 (411)(40), 2.92(332)(100), 2.539(600)(60), 1.792(604,660)(90) and 1.534(932)(80). Dcalc = 5.44(1) g · cm-1 for the empirical formula. The mineral is interpreted to have formed by metasomatic reactions of Sb-, Mn-rich fluids with a previously Si-depleted volcanite, followed by metamorphism under conditions of high fO2, silica undersaturation and relatively high T. The mineral name is for Urban Hiärne (1641-1724).