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PhotosDescloizite-Mottramite Series - Tsumeb West Mine, Tsumeb, Otjikoto Region, Namibia

30th Aug 2013 19:32 UTCRichard Gunter Expert

Mottramite, Cerussite

Tsumeb Mine (Ongopolo Mine), Tsumeb, Oshikoto Region, Namibia

If the RRUFF data on these "trees" is characteristic then the green aggregates are almost pure Mottramite and should not be put in the series.

30th Aug 2013 21:27 UTCRichard Gunter Expert

The Mottramit/Cerussit noted on the paper will look a little different than the Mottramite-Calcite intergrowth and more like the attached Duftite-Cerussite. The colourless crystals intergrown with the Mottramite trees are always Calcite as far as I have seen.

30th Aug 2013 22:16 UTCDebbie Woolf Manager

Agree Richard, Mottramite but from the Tsumeb mine not Tsumeb West mine.

Complaint sent.

30th Aug 2013 22:22 UTCA. A. Faller

Thanks for the heads up. The mine name has been changed. However, there are distinct cores of reddish-brown within the Mottramite, and have been I.D.'d as Descloizite...

30th Aug 2013 22:22 UTCA. A. Faller

Done. Thanks, Deb.

30th Aug 2013 23:03 UTCRichard Gunter Expert

That is interesting as my Mottramite sample's interior is always a deep greenish-black with a pronounced radial structure across the elongation of the tree. There may be more complexity here than has been noted so far. Debbie do you know of any literature on these Mottramite trees and their location within the Tsumeb deposit?

31st Aug 2013 00:03 UTCDebbie Woolf Manager

Not that I know of.

31st Aug 2013 00:26 UTCRichard Gunter Expert

That is too bad. Even though the sample is from W. Kahn the only locality is Tsumeb/SWA. He called it Mottramite xls on Calcite xls.

3rd Sep 2013 20:54 UTCErnst A. Schnaitmann Expert

Hi A.A.,

Can you please advise on how eh descloizite was ID'd? Visually?

Kindest regards

Ernst

3rd Sep 2013 22:30 UTCA. A. Faller

Sure, Ernst:

While on a trip to visit the Geology Dept. at a university here in Virginia, it was analyzed with an X-Ray Spectrometer.

3rd Sep 2013 23:54 UTCRichard Gunter Expert

Should the entry then be both Mottramite and Descloizite with Calcite since there seems to be a break in composition between the core and rim in this case rather than a continuous series as the current heading suggests. The exhaustive work by Boni et al in Economic Geology (2007) indicates the vanadium mineralization in the Otavi Mountain Land occurs as discrete groups of compositions and not as a continuous series. The detailed description of the vanadium mineralization in the Mineralogical Record v. 28 no.2 reaches similar conclusions.

4th Sep 2013 00:15 UTCA. A. Faller

Richard:

This actually sounds like a suitable solution for identifying the specimen. Thanks for the input. I'll wait for other feedback, though, if you don't mind, (partly just because I'm actually enjoying this since it's one of my favorite pieces) seeing as how I've been robustly indulging in references and other example photos.

4th Sep 2013 15:15 UTCRichard Gunter Expert

Sounds good to me. Happy to be of help.

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