Bournonite (“cogwheel”) on matrix blue-green this attractive three-dimensional “mound” of

this attractive three-dimensional “mound” of black “Marmatite” Sphalerite is comprised of sharp

there are a few rough spots here and there

which is not often found in well-crystallized display specimens

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

Bournonite (“cogwheel”) on matrix blue-green this attractive three-dimensional “mound” ofFinding 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