Bournonite (“cogwheel”) on matrix blue-green Specimen # BOL711B255

Specimen # BOL711B255

modified scalenohedra of Calcite sitting on underlain "chlorite" on matrix

No damage to the Brookite and just beautiful in person

It's not completely unstable like decomposing Limonite and it provides a much more appealing contrast than ordinary Pyrite

there are a few rough spots here and there

Bournonite (“cogwheel”) on matrix blue-green Specimen # BOL711B255Finding 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