Ettringite

Unknown Owner

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This unusual elongated crystal specimen appears 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. It is slightly etched and matte compared to other crystals here. 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 well. 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!