This specimen features three minerals, lorenzenite, nenadkevichite, and gaidonnayite, each of which is moderately uncommon to somewhat rare at MSH. But finding them together is a very rare event. In addition, the small lorenzenite needles all grow on a dark amphibole (perhaps arfvedsonite), which, in and of itself, is highly unusual.
According to the most recent MSH rarity tables (Lapis and Rivista Mineralogica 2000), lorenzenite is found almost exclusively in the igneous breccia and hornfels environments. But both nenadkevichite and gaidonnayite are extremely rare in breccia and only gaidonnayite has been reported – very rarely - from hornfels. This specimen is from veins in hornfels very near the Poudrette pegmatite. Perhaps one could call it “becciated hornfels”.
Of course, the Lapis/Revisat rarity tables are out of date, and the whole “MSH environment scheme” presented there has been extensively modified since then. Nonetheless, this is a very unusual specimen.
Moreover, both the lorenzenite and nenadkevichite have been verified via qualitative EDS (to the extent that that is possible). In addition, the Ti and Nb peaks for the nenadkevichite are nearly equal. Since Ti is detected more readily than Nb, this is probably still nenadkevichite rather than korobitsynite (or tsepinite-Na), but only WDS could tell for sure. (My money is on nenadkevichite.)
Note: Lorenzenite and vinigradovite can look similar and have similar chemistry. It may be difficult to distinguish them via qualitative EDS. However scan #157 for the lorenzenite has a distinctly lower Si peak (relative to Ti) than scan 289X , which is for a ‘known” specimen of vinogradovite. In fact, the Si peak heights have precisely the ration one would expect from the chemical formulae. (The lorenzinte also has Nb, which is not unusual – see the “Handbook” – but the peak does look unusually high.) See the “Analysis” tab.
Examples of both the lorenzenite and the gaidonnayite are shown in the first two pairs of photos (FOV 1.9 x 2.5 mm and 3.2 x 2.3 mm resp.) The bronzy lorenzenite needles are <= 0.4 mm long. The larger gaidonnayite aggregate spans 0.65 mm. Individual gaidonnayite crystals are <= 0.4 mm. These are small crystals. You will need 30X to see them clearly. But many are extremely sharply and beautifully formed. The dark prism are an amphibole (possibly arfvedsonite, but given the “breccia-like” environment, perhaps some sort of richterite.)
The next two pairs of photos (FOV 2.5 x 1.9 mm and 2.3 x 3.4 mm resp.) show two slightly different views of the colorless nenadkevichite (1.4 mm) with more lorenzenite (0.35 mm) on amphibole and more gaidonnayite.
This is not a delicate specimen. Single item shipping weight (no case) is 3.8 oz (108 g). For shipments outside the USA, up to a total weight < 8 oz (225g), this can be combined with items from this or other auctions for the same postage.
Within the USA, postage increases by about $0.20 per ounce. Above 13 oz, I will use Priority Mail (ca $9.25 including packing - varies by destination).