This is a very complex specimen, with very interesting examples of several MSH rarities, including adamsite-(Y), for which MSH is the TL. The significant species have all been analyzed via qualitative EDS (to the extent that that is possible). See the “Analysis” tab. For a discussion of each ID, see the corresponding photo(s). Most of the minerals are micro, but the adamsite-(Y) after shomiokite-(Y) is clearly naked eye visible.

The first photo (FOV 6.8 x 4.6 mm) shows the adamsite-(Y). It is fairly clear that it is replacing shomiokite-(Y) (which is a common thing at MSH), but I don’t know if any shomiokite is left. Both minerals are very rare at MSH. The little round bumps on the right end are basntnäsite-(Ce), which is “medium rare” at MSH.  But this is not a significant example – I had it analyzed just because I was curious. The sample I sent had some adamsite-(Y) attached, but got crushed in the mail, so scan #309 shows a mixture of these two minerals. The Na and Y are due to the adamsite, and most of the Ce, La, and Nd are due to the basntnäsite. (Note that Y and, especially Na, are not as easily detected by this equipment as the LREEs, so their relatively low peak heights are misleading.)

The next pair of photos (FOV 4.4 x 6.5 mm) shows the basntnäsite end of the adamsite PSM more clearly. (Please note that one of the basntnäsite “bumps” was removed for analysis.) The adamsite PSM sits on a smoky quartz crystal and is surrounded by little “sausages” probably parisite-(Ce) with donnayite-(Y) and/or synchysite-(Ce) inter-growths.

Two scans for samples from different cavities showed somewhat different chemistry. When immersed in HCl, there is a brief period of vigorous effervescence, after which a gray, spongy, blob is left behind. Presumably the effervescence is due to the donnayite (or synchysite) and the gray residue is parisite (which is insoluble in HCl).

Scan #308 is for the “sausages” in this cavity. Modulo the fact that this is just a qualitative scan, the best interpretation is an intergrowth of paristite-(Ce) and synchysite-(Ce).

Scan #263 is for similar, but translucent, “sausages” from the cavity shown in the next pair of photos (FOV 2.4 x 3.5 mm). Scan #263 seems closer to synchysite than to parisite, but the habit is very strange for synchysite at MSH. The presence of Na, Sr and Y in scan #263 suggests that these crystals may have a donnayite-(Y) component. In that case, syntactic intergrowth of parisite and donnayite would be a better fit. That could also account for the strange habit. But, apart from the apparent presence of a donnayite component, scan #263 is essentially identical to scan #128 , which is for a very typical MSH synchysite

Scan #263 could also be interpreted as calcioburbankite or even as rémondite-(Ce) – compare with scan #272. But neither calcioburbankite nor rémondite-(Ce) would account for the insoluble residue in HCl.  Other interpretations (such as inclusions in calcioburbankite) are possible, but it seems more reasonable to interpret all of the “sausages” as variations on a single “theme”, namely parisite-(Ce).

As shown in the next photo (FOV 1.4 x 2.1 mm), some of the translucent “sausages” are encrusted by tiny discs (< 0.2 mm) of a zeolite, proabably chabazite-Na. The EDS scan (#264) is very similar to that for “known” chabazite-Na from another find, and the habit is typical for chabazite from MSH. But other zeolites found at MSH could have similar scans. Zeolites can be very hard to pin down accurately. At a minimum, WDS would be required. That said, I think this is chabazite-Na.

The  next photo (FOV 4.4 x 6.7 mm) shows some of the eudidymite and epididymite on the specimen. The eudidymite diamond is 2.8 mm wide. Possibly there is epitactic epididymite growing on it. The free standing prisms are probably epididymite. Similar prisms on another specimen turned out to be intermediate nenadkevichite-korobitsynite, but analysis of one of the prisms in the next photo (FOV2.6 x 3.1 mm) showed epididymite. Of course epididymite and eudidymite are chemically identical, so EDS can’t tell them apart. (All you see in scan #261 is Na and Si, because EDS can’t see the Be.)  The prisms were analyzed to make sure that they were not nenadkevichite group. My IDs are based on the scans plus visual appearance.

But as shown in the next photo (FOV 3.7 x 5.9 mm), it is often difficult to tell eudidymite from epididymite visually. The crystals in this photo produced essentially the same scan (#262) as the more acicular prisms, but I’m not sure which of the two species they are. The photo also shows a particularly pale synchysite-parisite “sausage” 2.1 mm long.                    

Single item shipping weight (with MIN case) is 5.3 oz (150 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 (about $9.25 including packing – varies by destination).