Viboras Mine, Machacamarca, Machacamarca District (Colavi District), Cornelio Saavedra Province, Potosi Department, Bolivia
To find a fine quality "cogwheel" such as this on matrix from Machacamarca is not common, and the photos honestly do not do this piece justice as it is much more eye-catching in person. This piece features a few attractive "cogwheel"-twinned crystal groups of Bournonite with superb luster sitting atop a matrix of micro Pyrite, Quartz and Sphalerite. The "cogwheels" feature dozens of discreet, striated "cogs" that form the edge of the fairly thick metallic grey crystals. One side of the crystal is contacted where it more than likely was removed from the host rock, but the piece in general is in very good shape.