Oxide, antimony-bearing mineral
Specific gravity: 5.13 calculated
Hardness: 6 to 7
Colour: Black, (translucent dark red)
Occurrence:approved in 2000
At the type locality, the Garpenberg Norra mine (North), Garpenberg, Hedemora, Dalarna County, Sweden, the deposit consists of zinc-lead-iron-copper-antimony-silver mineralised supracrustal units (marble and altered felsic volcaniclastic rocks). The sulphide ores, dominated by sphalerite, galena and pyrite, form lenses and veinlets in close association with dolomite marble and silicate skarn.
The peak conditions of metamorphism of the area are estimated to be temperature greater than 550°C and pressure less than 3.5 kbar.
The investigated sample, about 50 x 30 x 20 mm in size, was collected from a skarn enclave within dolomite marble. It is dominated by a reddish orange amphibole-rich assemblage, with individual crystal fibres up to 10 mm in length, in contact with granular dolomite and calcite. The dominant species is manganese-bearing tremolite, which commonly contains patchy inclusions and overgrowths of zinc-bearing clino-suenoite. The latter mineral is suspected to be responsible for a rather intense yellow-orange response of the assemblage in ultraviolet light at a wavelength of 254 nm. The amphiboles are intimately associated with minor amounts of manganese-bearing talc. Irregular black clusters in the rock consist mainly of franklinite and rinmanite. Microscopic amounts of baryte and svabite also have been detected.
Rinmanite occurs both as isolated crystals within the silicate matrix, commonly adjacent to talc, and in aggregates lining franklinite (CM 39.1675-1685).
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