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Faujasite-Na With Donnayite Group Phillipsite-Na & Muscovite

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LMB613560

Faujasite-Na With Donnayite Group Phillipsite-Na & Muscovite

Rare Mineral

Description Tabs

Description
Locality: 
Poudrette Quarry, Mont Saint-Hilaire, Québec, Canada
Class: 
Crystals on Matrix
Size Range: 
Thumbnail (1-3cm)
Size: 
0.5 × 1 × 1 cm
Description

World wide, faujasite-Na is a rare mineral, known mostly from the Limberg quarries in Germany, and Tenerife in the Canry Islands. It is exceedingly rare at MSH, the only verified occurrence being a very localized find in the Poudrette pegmatite complex. This is a very small sample from that find.

The sample has not been analyzed, firstly because it would be too expensive. (EDS is far from sufficient. At a minimum, WDS would be required.) Secondly, there isn’t anything to spare for an analysis. And even if one attempted to somehow get by with an analysis of the crystals on matrix, there is a very good chance that the faujasite would dehydrate in the SEM chamber and turn white.

The faujasite ID is based on visual similarity with known faujasite  which was found in the same area (albeit three weeks earlier) and in the same association. I am pretty sure that this is faujasite-Na, but I cannot guarantee it. That’s the best I can do. But you are not likely to find any other faujasite-Na from MSH with better “credentials.”

In addition to the faujasite-Na, the specimen has small but nice crystals of phillipsite-Na and very tiny crystals of yellow-tan muscovite. These two minerals, in the same habits, are also found with the verified faujasite-Na. (However, many other specimens found nearby, but not having faujasite-Na, also have these minerals with the same habits. By itself, this association just means that the specimen is probably from the right general area, not that it is necessarily from the faujasite find.)  There is also a donnayite group mineral (probably mckelveyite-(Y) or a Ba rich donnayite-(Y)), but the habit is somewhat different from that found with the known faujasite.

Lastly there are a few tabular crystals of a very dark mineral that, in some ways, looks like columbite-(Fe), which was also found nearby (but not on the faujasite specimens), but in other ways looks like very dark synchysite-(Ce) which was also found nearby. There is not enough of this material to spare for off-matrix analysis, and, as mentioned, on-matrix analysis would probably ruin the faujasite. So I make no claims about this mineral.

All of these minerals are shown in the first three pairs of photos (FOV 1.7 x 1.1 mm, 1.85 x 1.25 mm, and 2.05 x 1.2 mm resp.), which are all just slightly different views of the same small cavity, but with the lighting arranged to emphasize different features. Note that these are all very small objects. You will need 30-50X to view them adequately.

The first pair of photos highlights the small (0.2 mm) faujasite octahedron in the center. It is twinned in a characteristic way. The faujasite sits on muscovite. The “donnayite group” crystals are on the right, and phillipsite-Na is on the left. Beyond the phillipsite are the dark, unidentified, tabular crystals. (There are a few of these mixed in with the muscovite as well, but they can’t be seen clearly.)

One expects faujasite to be octrahedral – as at Limberg. But, while there are, in fact, ctahedrons on the known faujasite specimens, much of the faujasite at MSH is so heavily twinned that the basic ocatahedral form is not evident.

The second pair of photos highlights a larger faujasite aggregate that is actually more typical. The highlighted face is particularly characteristic. Compare with the photos of verified MSH faujasite-Na posted on Mindat.

The third pair of photos highlights the “donnayite group”. (The muscovite came out too green in this photo – not sure why.) Similar material from nearby finds produced EDS scans consistent with mckleveyite-(Y) or something intermediate between mckelveyite-(Y) and donnayite-(Y). These nearly colorless crystals have shapes typical of mckelveyiite, but they were not analyzed.  The little blobs are pyrite sprinkles.

Finally, the fourth pair of photos (FOV 1.0 x 1.25 mm) tries to clarify the morphology of the dark tabular crystals. The color and iridescence are similar to that seen on some samples of columbite-(Fe) (and –(Mn)) from nearby finds (made about two weeks later). But the shape appears to be hexagonal – as in synchysite-(Ce). Of course, many orthorhombic minerals have pseudo-hexagonal habits, so the crystals might still be columbite. (Both colubite-(But in the absence of analysis, I make no claims.

Single item shipping weight is 2.7 oz (77 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). 

Mineral Data
What's on the rock

Faujasite-Na

Formula: 
(Na2,Ca,Mg)3.5[Al7Si17O48]·32H2O
Strunz: 
9.GD.30
Crystal System: 
Isometric
Hardness: 
5.0
Type Locality: 
Limberg Quarries, Sasbach, Kaiserstuhl, Baden-Württemberg, Germany

Phillipsite-Na

Formula: 
(Na,K,Ca0.5,Ba0.5)4-7[Al4-7Si12-9O32]·12H2O
Strunz: 
9.GC.10
Crystal System: 
Monoclinic
Hardness: 
4.0 - 5.0
Colour: 
White
Streak: 
White
Type Locality: 
Rupe di Aci Castello, Aci Castello, Etna Volcanic Complex, Catania Province, Sicily, Italy

Muscovite

Formula: 
KAl2(AlSi3O10)(OH)2
Strunz: 
9.EC.15
Hardness: 
2.5
Streak: 
White
LMB minerals

Seller Information

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Seller's terms and conditions

In addition to the standard terms and conditions, please note the following. Almost all IDs are visual. While in most cases the ID is obvious, there may be cases where it is not. If you are doubtful about a particular ID, please ask for more information. Or do not bid! Similarly, if you are not sure that the specimen meets your criteria, do not bid. I have tdone the best I can with the photos. Nevertheless, if you are not happy with a specimen for any reason, I will refund the bid price – but not the shipping costs (unless the fault is clearly mine) – if the specimen is returned. This policy applies even if analysis of the specimen shows that my ID was incorrect. When in doubt, ask - or don’t bid. Note that most crystals at MSH and Varennes are micros - even if on large specimens. Please pay attention to the stated sizes. Any customs duties, fees etc. are the responsibility of the buyer.