Abstract

Freedite and thorikosite are new mineral species, which are closely related structurally and chemically to one another and to the synthetic bismuth oxyhalides.

Freedite, Pb15(Cu,Fe)32+As43+O19Cl10, is monoclinic, space group C2, Cm, or C2/m, with a = 13.569(5), b = 20.085(4), c = 7.463(4)Å, β = 105.75(5)°, V = 1958(2)Å3, and Z = 2. Freedite is greenish-yellow, with vitreous luster, {100} cleavage, and a specific gravity of 7.0 g/cm3 (obs). It is found associated with ecdemite, lead, copper, finnemanite, and calcite at the Långban Mine, Värmland, Sweden. The species is named in honor of Dr. Robert L. Freed of Trinity University.

Thorikosite, (Pb3Sb0.6As0.4)(O3OH)C12, is tetragonal, space group I4/mmm, with a = 3-919(1), c = 12.854(5)Å, V = 197.4(1)Å3, and Z = 1. Thorikosite forms light yellow prismatic crystals, tabular on {001}, with perfect {001} cleavage, vitreous luster, and density of 7.24 g/cm3 (calc). Thorikosite occurs associated with hydrocerussite, paralaurionite, sphalerite, and calcite in the slags of Laurion, Greece.

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