Bournonite, Quartz and Pyrite
Pachapaqui District, Bolognesi Province
7.2 x 5.4 x 5.2 CM (cabinet)
Late Summer 2018
Two-sided specimen with excellent sharp Bournonites on both sides. All the Bournonites show bright silver luster and twinning that in some crystals has the classic cogswheel habit. The side I consider the "front" or better display side has two main Bournonites that are perfectly formed and undamaged, set off by golden Pyrite and milky Quartz crystals. The "back" side has more nice Bournonites but there is some damage and contacts, (that is why it is the back of course). A few years ago matrix Bournonites of this quality were very rare and expensive when available but both China and Peru then began to produce these and they became very affordable. Now both these sources are not producing.
A well exposed Bournonite with complex twinning sits well exposed on a sulphide matrix with Dolomite crystals. Ex Charles Noll collection, this is a choice, old specimen from the classic locale of Pribram. The central crystal is 2.6 CM across., and has a few small Quartz crystals scattered on it. In unusually good condition as seen, the surface is also lustrous and has a fine patina.
A killer Potosi Bournonite with large, perfect crystals showing classic form. Complete all around, a perfect floater with no matrix, just big metallic Bournonites in fine condition. The largest crystal is a sizable 3.8 CM and all the crystals have a gleaming gunmetal luster. This is from the remarkable find in 2007-8 which had the very best Bournonites ever seen from Bolivia and some of the best ever found on the planet. This is very much a top percentile specimen from that discovery, a true top shelf piece.
Bournonite on Quartz
Yaogangxian Mine, Yizhang County
8.8 x 4 x 3.2 CM (cabinet)
new june 17
A lustrous Bournonite is perched on one end of a doubly-terminated Quartz crystal from Yaogangxian. Remarkably, the entire specimen is fully crystallized and complete on all sides, it is a floater. A modern classic specimen- vintage 2004, the great era of Yaogangxian production. The Bournonite has well defined crystal faces on the front side, however the back side is less distinct, more complex, yet still perfect and undamaged.
Bournonite - classic Cornish
Herodsfoot Mine, Lanreath, Liskard District
3.9 x 3.1 x 2.1 CM (miniature)
Post Tucson 2015
A nicely crystallized cluster of cogswheel form Bournonite from the famed Herodsfoot Mine. An old specimen (pre 1950 but likely far older), the color is a dark "gunmetal" metallic black. The crystals have several habits and reach 1.6CM. There is damage on the edges and minor chipping but the central area of this is in good condition. Overall nice specimen of this delicate mineral from this old classic Cornish locale.
Yaogangxian Mine, Yizhang County
3.4 x 2.6 CM (small miniature/ large thumbnail (toenail))
We have all seen a lot of Bournonite from Yaoganxian, some is world class, but most has a lot of serious damage. Clean examples of this brittle mineralare quite rare, and to find a nearly pristine "cogswheel" type that is crystalized all around (floater) is very special. This complex cluster has excellent mirror bright metallic luster, great form and esthetics. Very careful examination shows a few hard to find chips all under 1 mm in size, not distracting at all. For some reason, there have been more single, prismatic type crystals from Yaogangxian, this example looks much more English than Chinese! Super reasonable !
A very large, lustrous cogwheel type Bournonite (over 5 CM across) that is complete sitting on Fluorite and Quartz crystals one of which penetrates the Bournonite. A exceptional example from Yaogangxian, recognized as the worlds best location for this specie. Some of the fluorite and quartz have damage especially at the edges of the piece, but overall the condition is superb. This sits upright and perfectly without assistance, and the esthetics are top shelf. Given the fragility of large bournonite, the quality and completeness of this crystal is even more remarkable. Add the Fluorite for a color accent (and an uncommon association) the whole is highly desirable.
A wonderful esthetic for a dark mineral like Bournonite is to be displayed on on colorful matix, and this piece does that well. Several sharp, prismatic and lustrous silvery crystals of Bournonite are well placed on a sparkling purple fluorite and quartz mixture. A few matted hairs of Boulangerite are in evidence as well. There is one Bournonite that is broken off (not very distracting tho) all the rest are quite clean by eye and only show some edge chips at 10X magnification. A very good matrix Yaoganxian piece and a good value.