This specimen features very intriguing pseudomorphs of high Mn siderite encrusted by tiny , apprarently epitactic, crystals of apatite (most likely fluorapatite). "Sandwiches" of elpidite and menadkevichite are probably familar to most MSH collectors. But these “sandwiches” are completely different. Yet another example of the many perplexing pseudomorphs found at MSH. Possibly this is a unique find.
The siderite and apatite have been verified via EDS. (See the “Analysis” tab. On some specimens, the siderite is quite pink and may be Mn dominant – i.e. rhodochrosite.) The precursor is not known. Morphologically, the aggregates are reminiscent of nenadkevichite, lanthanite-(Ce), or perhaps petarisite or vuonnemie, but is hard to see how any of these could turn into siderite encrusted by apatite. However, it is very unlikely that the siderite is not pseudomorphous. But note that these are “micro-pseudomorphs”. You will need about 15X to view them. (50+X to see the apatite crystals.)
The specimen is from a pegmatite that was very rich in clear, glassy, “jack-straw” elpidite, pink transparent albite, small “sunbursts” of aegirine, and small smoky quartz phantoms. (There is only a bit of elpidite and no quartz on this small specimen).
The first pair of photos (FOV 1.35 x 2.0 mm) is a close-up of one of the “sandwich” aggregates. The epitactic apatite prisms are only 0.05 mm long. (EDS can only identify “apatite”, since F can’t be seen, but fluorapatite is the only “aptite” on the current MSH species list. “Carbonate fluorapatite, which is, in any case, just a variety, isn’t very likely.) The dark point crystal on the bottom is aegirine.
The second pair of photos (FOV 6.7 x 4.1 mm) is a broader view showing more of the “sandwich” aggregates. The clear prisms and fibers are elpidite.
The third pair of photos (FOV 6.2 x 4.5 mm) shows the nicest group of pale pink albite crystals. The largest crystal is 3.8 mm. There are a few other well-formed albite crystals nearby (not shown).
Single item (small box) shipping weight 3.1 oz (87 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”, 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 Mai. The rate (including packing) is ca $9.25 (varies by destination).
