Forget rare minerals. MSH is the kingdom of strange (and rare) pseudomorphs. And this one is about as strange as it gets. It is hard to believe, but the pearly foliated plates are zircon - as attested to by both EDS and XRD. (See the “Analysis” tab for an EDS scan.) By itself, the qualitative EDS scan isn’t completely unambiguous, and the presence of Ca hints at something more exotic than zircon. But XRD doesn’t lie, and it was confirmed as zircon via PXRD at two different research labs. The Ca in the EDS scan may have come from admixed calcite.)
Presumably these are PSMs, but it is not know what the precursor was. One possibility, catapleiite, was regarded as both plausible and (geochemically) implausible by two different mineralogists. In any case, a most unusual item.
The first pair of photos (FOV 6.6 x 4.2 mm) shows a “sheaf” of platy zircon about 4 mm in maximum diameter. The background is siderite with a crust of another carbonate (possibly ankerite).
The second pair of photos (FOV 3,7 x 6.2 mm) shows another zircon “sheaf” at he bottomt. Here the surface looks as if the aggregate were formed from bladed crystals (but I don’t think that’s the case.) In the center are small honey colored fluorite cubes and at top are some nice albite blades.
The next photo (FOV 3.2 x 4.5 mm) is a clearer view of the surface patterns on the fluorite. The longest edges are 0.65 mm. There are other fluorite crystals on the specimen, but it is just an accessory mineral.
The next pair of photos (FOV 3.7 x 6.2 mm) shows a larger aggregate of “zircon” of a deeper yellow color (perhaps a stain). There are other zircon “folia” on the specimen. The photos show the most interesting ones.
Other minerals visible in the full view photo, besides the zircon “folia”, are albite (laths), microcline (broken blocky crystals), fluorite, and siderite, possibly with a crust of ankerite. Ankerite is a rare mineral at MSH, and this is one of the typical habits (i.e. crusts on siderite). But it has not been analyzed.
The specimen is from an “early” part of the Poudrette pegmatite that was rich in excellent gaidonnayite. Found July 1994. I have only a few of these. This is perhaps the richest example.
Single item shipping weight is 4.0 oz (113 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 ($9.25 including packing).
