Bournonite (“cogwheel”) on matrix blue-green all the way to tan

all the way to tan / brown Siderite at the other end of the series

No damage to the Brookite and just beautiful in person

This material is rarely seen in today's market and this particular specimen is at least 35 years old

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 all the way to tanFinding 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