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Identity HelpNsutite question
13th Sep 2018 21:09 UTCRolf Luetcke Expert
I purchased this specimen from the micro mounters room at the Tucson mineral show and the label said nsutite and the specimen had these long, black crystals that were silvery metallic from the side. Sure doesn't look like any of the nsutite photos and the Tres de Mayo Mine in Arizona doesn't have the mineral listed. Since it is a tiny specimen, an analysis is not happening. Hoping someone has a bit of an idea what these crystals may be.
13th Sep 2018 22:12 UTCRolf Luetcke Expert
13th Sep 2018 23:09 UTCRichard Gunter Expert
13th Sep 2018 23:35 UTCKeith Compton 🌟 Manager
I can't really comment on either the brown or the black material but it is unclear to me which you think may be nsutite. If you are asking if the black needles are nsutite then from the literature I would presume no.
The brown material may be nsutite:
From the following reference: Zwicker, W.K., Groeneveld Meijer, W.O.J., Jaffe, H.W. (1962) Nsutite - a widespread manganese oxide mineral. American Mineralogist: 47: 246-266.
It is commented that: "It is doubtful whether nsutite can be identified from a megascopic examination alone. Shrinkage cracks, however, which are somewhat diagnostic for nsutite in polished sections, give massive specimens, such as that from Tartana, a strongly developed columnar jointing. The Morro da Mina [Lefaiete District, Minas Gerais] material is a soft, brown' earthy mass, whereas numerous samples from the Nsuta mine are fairly hard, metallic gray, porous aggregates".
"Characteristic of many occurrences of nsutite is its proximity to manganese caronbate. In some occurrences manganoan nsutite forms replacement veinlets in manganese carbonate rock. It then appears to be among the first oxides forming from the oxidation of manganese
carbonate along with birnessite".
Although the brown on your specimen looks more like a coating on something.
Then again the black blebs in the lower left of your second photo?
14th Sep 2018 10:03 UTCAlfredo Petrov Manager
The brownish crust on Rolf's photo is certainly not nsutite, and it might be rhodochrosite. The black needles might be a different Mn oxide, perhaps a member of the cryptomelane group? "Psilomelane" seems to be abundant there, according to the mines' description on Mindat, and "psilomelanes" are most commonly cryptomelane group members.
14th Sep 2018 13:17 UTCRolf Luetcke Expert
I realize this piece is one that should be among my ? specimens since there is little I can do but thought the long needles were quite interesting. I wanted to see what others think and I sure appreciate the input.
Alfredo, I had thought of psilomelane also but that is normally much thinner and I had never seen psilomelane in such nice and stiff crystals. An interesting mystery piece.
Thanks all.
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 20, 2024 02:12:40