This very unusual specimen hosts well defined crystals of wurtzite (a great rarity for the Saint-Amable sill), very dark (“sinister” looking!) yofortierite, and numerous short-prismatic crystals of natrolite. The wurtzite was analyzed via qualitative EDS. (See the “Analysis” tab.) Of course EDS can’t tell wurtzite from sphalerite, but many of the crystals have clearly hexagonal cross-sections and have habits similar to some wurtzite from other localities. See below for additional comments on the wurtzite ID. The yofortierite was not analyzed, but it is much too dark to be tuperssuatsiaite from this locality. The natrolite is typical of the quarry. It is mostly very inter-grown. (It may be a pseudomorph in part.)
The first pair of photos (FOV 1.2 x 1.75 mm) is a close-up of some of the wurtzite crystals. The hexagonal form is most evident in the crystal at center. Note also the “stacked” appearance of the crystals, which is typical of wurtzite (e.g. Carrara, Uchucchacua, Llallagua, etc).
The second pair of photos (1.35 x 2.0 mm) shows some of the same crystals from a different angle. In this photo, the hexagonal form is more evident in the crystals at top. Reflections make the ”stacking” (striations) more evident in all of the crystals.
The third pair of photos (FOV 2.45 x 3.0 mm) is a broader view. In this photo, the hexagonal form is evident in the crystals at top and bottom.
The next pair of photos (FOV 4.2 x 6.5 mm) is a close-up of some of the “sinister” yofortierite. Recent analyses have shown that much of the lighter colored “yofortierite” in the sill is actually tuperssuatsiaite or “tuperssuatsiaite-like”, but I think that this stuff is much too dark for that. On the far left of the photo are very inter-grown crystals of natrolite, apparently replacing a large crystal that has the morphology of sodalite. Away from the “edge” of this precursor crystal. The natrolite crystals grow freely (but are still very inter-grown). The next photo (FOV 4.2 x 5.0 mm) shows the best group of these. (But lack of contrast makes for a photo that isn’t very clear. The crystals will be better visible with a binocular scope.)
In the full-view photo, the “sinister” yofortierite is at top. The blue-gray area below the yofortierite is maostly natrolite. The arrow points to the wurtzite. The white stuff appears to be very corroded analcime. It was not analyzed.
Regarding the wurtzite ID: It is true that sphalerite can form platy aggregates. Nor (absent XRD) can I prove that these aren’t pseudomorphs of sphalerite after wurtzite (or even some other mineral). But I don’t think either possibility is plausible in this case. It is also true that wurtzite (e.g. at nearby MSH) has little if any Fe, whereas the scan for this sample shows “noticeable” Fe. However, wurtzite from Llallagua supposedly has plenty of Fe (and Mn), so I don’t think the presence of Fe necessarily precludes wurtzite.
Single item shipping weight (no case) 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 for total weights up to 13 oz ranges from $4.25 to $6.50 (including packing etc) regardless of destination. Above 13 oz, I will use “own box” Priority Mail. The rate, including packing, varies by destination from $7.25 to $9.50.
