I had never before seen, in person, a Cruciform twinned bournonite. However, I had read about them occurring in the mid 1800s at this classic mine for the species, long known as the world's finest source of bournonite. This was purchased in the 1980s and stashed away in Richard Kosnar's collection along with a small suite of other fine English minerals. This is a superb miniature. It is hard to imagine, for overall aesthetics and uniqueness, a more interesting English bournonite in this size range. It is pricey as heck, no doubt. But I am told only a few of these exist and this is complete all around 360 degrees, pristine, and meets any modern standard that you can hold an antique piece up to challenge - such are rare enough.