This is a superb example of the world class bournonite from Yaogangxian, which has redefined what a collector can own for the species. At the very top of its game, this mine's bournonites are, to me and most others, the most beautiful in the world. This piece has the top luster (so bright and metallic, it looks unreal, like polished aluminum). It has a very slight surface oxidation that, in certain angles only, gives it a rainbow shimmering on the frontal surface. The crystallography is complex and geometric, showing a cogwheel -like form. Most bournonites of this size are broken off matrix, but this has a stunning association with water clear, gemmy quartz points.A quartz crystal impales the bournonite, too, making for an unusual accent in the middle of the specimen. It is simply difficult to convey in photos, though we have tried (Joe Budd photograph from the frontal view). I would say that for the quality and size, it would be hard to do better even in the next higher price range. This piece is of magnitude enough to be not upgradeable in any easy sense, and to represent among the best of the species from this mine. As an added note, the bournonites come from old tunnels mined out in the 1950s-70s and to obtain them, artisan miners must travel up to those old levels in the dark, through very dangerous and unsupported tunnels. The remainign bournonite is in the pillars, so pillar-robbing must be practices to retrieve them, leading to a weakening of the supports for the old levels. Sadly, this resulted in tragic deaths in 2007, when a number of miners died. The government clamped down on official access to those levels, I am told. Nevertheless, even if people go in and find more, so few have been found of this caliber