Bournonite
Bournonite is a sulfosalt mineral recognized among collectors for its crystal form and distribution, with notable Chinese occurrences.
About Bournonite
Bournonite is a sulfosalt mineral in the bournonite group and has the chemical formula PbCuSbS3. It crystallizes in the orthorhombic system and is relatively soft, requiring careful handling. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.
Identification & care
Specimens usually show prismatic crystals; 'cog-wheel ore' — distinctive cruciform or gear-wheel shaped cyclic twins; tabular. Its color is typically steel gray, iron-black and lead-gray. The luster is metallic, sub-metallic, the streak is steel gray to black, and specimens are typically opaque. The cleavage is imperfect on {010}. The fracture is subconchoidal to uneven, which aids identification.
Collector context
How it forms
The geological setting for Bournonite is typically medium-temperature hydrothermal vein deposits with galena, sphalerite, tetrahedrite. It is commonly found in association with galena, sphalerite, tetrahedrite, chalcopyrite, pyrite, siderite, calcite.
Classic Chinese localities
Documented Chinese occurrences are recorded at Dachang ore field and Yaogangxian W-Sn ore field, among others.
Why collectors care
Collectors pursue Bournonite for the clarity of its crystal form and, in good material, saturated color that reads instantly across a display case. A well-terminated bournonite on clean matrix photographs well, identifies quickly, and anchors a cabinet piece. Top Chinese specimens over the last two decades have reset the bar for what bournonite looks like at collector grade.
What affects value
Value in Bournonite is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.
Naming history
The name Bournonite has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.