This specimen features interesting examples of several rare minerals: epididymite, “pyrochlore”, rhabdophane-(Ce) and lorenzenite, along with pink albite, aegirine, polylithionite, and “bitumen”. The epididymite and “pyrochlore” are abundant and the latter has very unusual chemistry (see below). Rhabdophane is a very minor accessory, but also has unusual chemistry. The lorenzenite is also a minor accessory, but it is of interest because it is extremely rare in the pegmaties at MSH.
Caveat: The scan is a good fit for lorenzenite. Vinogradovite would probably produce a similar scan, but I would expect the Si peak to be higher relative to the Ti peak in that case. However, this was a quick and dirty EDS scan, so comparing peak heights is risky. To be 100% sure, PXRD is probably needed. I didn’t feel that the cost of PXRD was justified in this case. (Supposedly the yellow SW UV response of lorenzenite is a a fairly reliable way to distinguish it from vinogradovite at MSH. But the crystal are too small to be useful for such a test.)
If you are willing to consider vinogradovite, then korobisynite might be another candidate. (In fact, some of the crystals look orthorhombic to me.) I very much doubt it, but if that's what it is - congratulations!
In any case, whether it is lorenzenite or vinogradovite, it appears to (mostly) epitactic on aegirine. A most unusual occurence.
There are many things to look at so not everything is shown.
MSH is well known for beautiful trillings of epididymite. But there are many other habits, perhaps less well known. This specimen feature numerous “hedghehog” aggregates and single crystals. The individual crystals are small (<= ca 1.5 mm), but well-formed and quite beautiful. The first five photos show examples of some of these crystals. There are many more groups on the specimen. Some of these photos also show “pyrochlore” and pink albite. The epididymite from this find was verified via PXRD at Laurentian University. This specimen has the best epididymite from this find.
The first pair of photos shows two, essentially single, crystals with different, perfect terminations. The blocky pinkish crystals on the left are albite. FOV in the photos is 3.3 x 2.1 mm.
FOV in the second pair of photos is 2.7 x 4.2 mm. The epididymite crystals are <= 1.4 mm. The small “fuzzy” yellow octahedral crystals on black aegirine are encrusted “pyrochlore” (see below) – ca 0.25 mm. The blocky and tabular pinkish crystals are albite. The raggedy micaceous stuff is polylithionite.
FOV in the fifth of photos is 3.6 x 2.1 mm. Shown is part of a group of epididymite crystals that spans ca 11 mm in total.
“Pyrochlore” is uncommon but not rare at MSH. However the specific species occurring at MSH have not yet been sorted out. The “pyrochlore” on this specimen is rather odd. The initial interpretation of two EDS scans showed very elevated "Ta" peaks – in once case higher than the Nb peak, which would make it a member of the microlite group. (See the “Analysis” tab). After consultation with a mineralogist very familiar with MSH, it was concluded that the “Ta” peaks are actually Si – which apparently has a peak that is nearly indistinguishable from Ta in a scan of this sort. According to this expert, many previous analyses of “pyrochlore” from MSH have shown very high levels of Si. “Microlite” has not been reported from MSH. Accordingly, I have labeled the stuff as “pyrochlore group”.
The next pair of photos (FOV 3.6 x 5.9 mm) shows the richest aggregate of “pyrochlore” on the specimen. The pyrochlore crystals are very small, <= 0.25 mm. They are strung on agirine needles. The crystals have an unusual yellow color – perhaps due to the high Si. Note that both the “fuzzy” exterior and “naked” crysrtals showed very high Si, with the “naked” crystals having the most Si. . The pale pink crystals are albite.
Rhabdophane-(Ce) is “medium rare” at MSH, and occurs only as pseudomorphs. The precursor is unknown, but may be a mineral related to mckelveyite-(Y). (In one bizarre case, analysis indicates rhabdophane replacing polylithionite! So there amy be other precursors.) But the most interesting thing about this find is that, as determined by microprobe (Pavel Kartashov – IGEM), they are very high in Ca – nearly brockite in composition. Brockite is extremely rare at MSH. (But this is NOT brockite. The composition of the “Ce site” was found to be ((Ce.28 La.16 Nd.07 Pr.03 Eu.01 Gd.01 Sm.01)sum=0.56 Ca.33 Sr.10 Ba.01)sum=1.00. So even though Ca is the single most abundant anion, the material is REE dominant, with Ce being the most abundant of the REE.) Interesting stuff.
Unfortunately, this specimen only has one good “crystal” of rhabdophane, and it is very tiny, but well formed.The next photo (FOV 1.9 x 1.3 mm) shows the rhabdophane PSM. It is only a bit < 0.3 mm in diameter, but one can see (at 30-50X) that it is hexagonal or pseudo-hexagonal. It looks like a miniature “yurt”.
Finally, one of the arrows pointing to epididymite also points to some of the epitactic lorenzenite. The next-to last photo (FOV 3.1 x 2.2 mm) shows most of these crystals (<= 0.7 mm). Also in the photo are a few more “pyrochlore” crystals and some platy crystals (polylithionite?) encrusted by white stuff that appears to be a mixtrure of calcite and more of the “pyrochlore”. (It is not rhabdopahne.)
There is also a small blob of shiny black “bitumen” – probably pyrobitumen - on the specimen. Not really a mineral – just a minor curiosity. I couldn’t provide a photo – think “tar blob” – but there is an arrow pointing to it.
The full-view shows numerous arrows on the "front" of the specimen. there are alos several arrows on the "back". There is a lot to look at.
Single item shipping weight (no case) is 4.0 oz (113 g). For shipments outside the USA, up to a total weight of 8 oz (225 g), this could be combined with other items from this or future auctions for the same postage. If you wish to keep an “open box”, you must let me know.
For shipments within the USA, there is a nominal increase of about $0.20 for each additional ounce. Above 13 oz I will use “own box” Priority Mail ($9.25).
