This is a damned near unique specimen, the likes of which I personally have never seen. Logically, the alteration makes sense of course. But in practice, it almost never occurs. The silver is a coating of 1-3 mm, over remnant pyrargyrite....so one could say it is a partial or surface alteration, but a pseudomorph nonetheless. I was able to track down a report of a similar specimen, via a reliable source. But I have NEVER seen one for sale or even in a museum record. And, moreover, this is aesthetic and highly displayable! The old label from Mitch Gunell's Collection notes that he purchased it from the late, great Martin Ehrmann in 1940. Gunnell assembled what is widely considered to have been the most comprehensive pseudomorph collection ever, and this pedigree carries value. But, I feel the mineral is priced on its own merits in this case, with the pedigree as a bonus.