Ettringite

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This is a huge specimen, with more ettringite in one place than I have ever seen. It is really subtle in its beauty, with oyelite between the cracks in the crystals, providing a white web-work background on which the powder-lemon-yellow crystals stand out all the more dramatically. There is some damage to the edges of the large crystal cluster, where peripheral-facing tips are missing or there is a contact point. But the core cluster is very 3-dimensional, gemmy, and capped by the best terminated crystal: The large crystal in the middle is 10 cm tall, and has a freestanding termination. Charlesite is a close relative of sturmanite and ettringite, and my understanding is that most crystals of either of the two yellow and more common species are actually zoned, and are thus partial charlesite. However, this crystal seems to have a pure, clear core which I suspect is charlesite, perhaps pure. (not analyzed). Unusual, in any case! Even more than on other specimens in this lot, many crystals here appear to consist of a white charlesite crystal with an outer layer of powdery-lemon-yellow ettringite atop, from what I am given to understand about how these species form in a related series. The outer layer of colored ettringite is very thin, under 1 mm, and most of this crystal is therefore clear and colorless. These larger crystals (but not the smaller ones) are slightly etched and matte compared to other crystals in this pocket, perhaps part of the phenomena revealing the clear cores. I am sure all in this pocket are zoned in some degree to charlesite and/or sturmanite; but this one is distinctly different, with the totally clear core showing so nicely. A MUSEUM PIECE, in both size and visual impact, even for the public who will not care about the fascinating chemistry revealed here in a gigantic specimen of a very rare species. The backside of the specimen has hausmannite, hematite, and oyelite. 1.3 kilos.