Bournonite (fine ''cogwheel'' twins) on Sphalerite

Item Description

Bournonite is a well-known sulfosalt species, found in many world localities, but most crystals you'll see are typically single blades. A few world localities are well-known for producing excellent "cogwheel"-shaped twins, which is arguably the most desirable style for the species. The Machacamarca District in Bolivia has produced some of the finest examples of this beloved, yet uncommon lead copper antimony sulfosalt mineral in the last 25 years or so. These specimens are some of the largest, finest and most crystalographically impressive examples to come out of any mind in the modern era of mineral collecting. This piece is a showy and aesthetic example featuring a group of lustrous, well-formed, metallic, bright gun-metal colored, thick tabular crystals forming wonderful "cogwheel" twins, sitting on sculptural Sphalerite matrix with minor golden metallic Pyrite. There are a few contacted areas, so the piece is not 100% pristine, but it's still quite showy and fine quality for what it is. It's incredibly rare to find such a complete Bournonites on matrix from this area, especially a multi-twinned group like this with great aesthetics. Very rare and significant for what it is. Don't miss out, it's one of the better Bournonites from Machacamarca that we've had to offer in the auctions in recent months. Valued $1,750.
For reference, Bournonite was named after the French mineralogist Jacques Louis, Comte de Bournon. Interestingly, Bournon elected to name the species Endellionite in honor of St Endellion, Cornwall, England, the type locality for the species, but it instead was named Bournonite by Scottish mineralogist Robert Jameson (Jamesonite).