車輪礦

Bournonite is a lead-copper-antimony sulfosalt classically known as “cogwheel ore” (车轮矿) for its distinctive cyclic-twinned crystals that look like geared wheels. It is the single most architecturally distinctive sulfosalt species.

Occurrence in China

The Yaogangxian mine, Hunan is a documented Chinese bournonite locality that produces cyclic-twinned cogwheel crystals up to several centimeters across, often perched on quartz and chalcopyrite. Historic European localities include Cornwall (UK) and Neudorf (Germany).

Identification

Cyclic six-armed cogwheel twins on (110) are unmistakable when present. Without the twin morphology, distinguish from galena (cubic, brighter), jamesonite (fibrous/needle-like) and tetrahedrite (cubic tetrahedra).

Collector Notes

Bournonite specimens are valued by both metallic-mineral specialists and geometric/architectural-mineral collectors. Yaogangxian and Cornwall pieces top auction catalogs.