Roscoelite is a green mineral from the mica group that contains vanadium.
The chemical formula is K(V3+, Al, Mg)2AlSi3O10(OH)2.[2]
Crystals of roscoelite take on the monoclinic form, and are from the 2/m point group.
The appearance is semi transparent to translucent coloured olive brown to green brown. The lustre is pearly. The mineral shows pleochroism with X showing green-brown, and Y and Z axes showing olive-green colour. The mineral was named after Henry Enfield Roscoe who first produced vanadium metal.
with an angle between axes of β=101.0°. The tetrahedral cation-oxygen atom distance is 164.1 pm, The distance from the cation to the oxygen in the octahedral plan is 202 pm.[3]
In the Mt. Kare mine in New Guinea the mineral occurs with gold and is an important maker of gold deposits. The temperature of the geothermal fluid that deposited the roscoelite was from 127 to 167 °C (261 to 333 °F). The fluid contained a high level of salt and also contained carbon dioxide, methane, carbonyl sulfide and other minor amounts of rock forming elements.[5]
^Kelley, Karen; Armbrustmacher, Theodore; Klein, Douglas (2004) [1996]. "Au-Ag-Te Vein Deposits"(PDF). In du Bray, Edward A. (ed.). Preliminary Compilation of Descriptive Geoenvironmental Mineral Deposit Models. United States Geological Survey.
^Ronacher, E.; Richards, J. P.; Reed, M. H.; Bray, C. J.; Spooner, E. T. C.; Adams, P. D. (2004). "Characteristics and Evolution of the Hydrothermal Fluid in the North Zone High-Grade Area, Porgera Gold Deposit, Papua New Guinea". Economic Geology. 99 (5): 843–67. Bibcode:2004EcGeo..99..843R. doi:10.2113/gsecongeo.99.5.843.