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Improving Mindat.orgAlabandite, Postmasburg, South Africa

18th Sep 2009 00:26 UTCEmil Box

I wonder if the Alabandite from the Postmasburg, South Africa photos has been analysed.

From an old collection we have such black cubes with red Diaspore named as Bixbyite. At that time analysed by XRD and spectral analyses (AES?)

Pale brown crusts on the photos could indicate Fe.

Could it please be investigated.

Thanks and greetings from

Milo

19th Sep 2009 19:39 UTCUwe Kolitsch Manager

Messages sent.

http://www.mindat.org/gallery.php?cform_is_valid=1&min=89&cf_pager_page=2

21st Sep 2009 10:21 UTCSimone Citon Expert

This is compact, pseudocrystallized Alabandite with dark bronze color, low lustre, brownish-greenish streak and hardness (verified) >4. I have some alabandites from other localities (Romania, Mexico) and this is very similar indeed. The African Bixbyite I've seen (expecially in isolated lustrous small crystals from placers deposits), is totally black and much harder. Do you have a pic of your specimen? Simone

21st Sep 2009 18:18 UTCElmar Lackner Expert

Hello,

after i read this i'am investigating my 'Alabandite' specimen.

Photo : http://www.mindat.org/photo-73891.html

First i do an hardness-test. This stuff scratches my (empty) wine-bottle (6-6,5). After that i heat a peace to red-glow, no decomposing or smelling from sulphuric gases like SO2 or H2S appears. That rules out Alabandite. Bixbyite is now highest on the list. (And i have one mineral less in my sytematic collection :-( ). I change the description of the photo later.

Best regards

Elmar

21st Sep 2009 20:12 UTCJean-Francois Carpentier Expert

Hello

I had also several "alabandite" specimens from Postmarburg posted on Mindat a while ago (see attached picture).

Rik Dillen sent me a message, wondering if these were alabandites or rather Bixbyite, as he established for his specimens.

XRD and EDX-SEM of my two specimens also revealed these are Bixbyite and that no alabandite is indeed present in those sepcimens. So far, I have not seen any confirmed Alabandite from Postmarburg.

Jean-Francois

21st Sep 2009 23:18 UTCEmil Box

Hello,

@ Simone: does >4 means <5 ? Alabandite Hardness 3.5-4

Attached a quick, bad photo.

22nd Sep 2009 06:57 UTCSimone Citon Expert

Ohh, sorry, <4 (verified with a Fluorite). Simone

22nd Sep 2009 08:32 UTCSimone Citon Expert

Emil

Jean-Francois

Elmar,

yes, in my opinion yours specimens are Bixbyite: a bit brownish and with low lustre on the surfaces due to alteration, but good crystallized (note the small faces on the apexes of the cube, caracteristic of the Bixbyite) and high lustre on the fresh fracture.

I have re-photographed my specimen, is evident the difference: crystallization is barely defined (as normal for the Alabandite, very rarely well crystallized), rich association with Mangan-diaspore, relatively low lustre all around. Again leaves slight signs on the Calcite and no strip the Fluorite, 3,5 - 4 infact is its hardness. I don't know if the Elmar's brownish material associated with the Diaspore of the same locale (http://www.mindat.org/photo-73868.html) can be Alabandite, try another hardness-test, Elmar! Ciao. Simone

(PS for Jean: do you have seen what a super Destricella Hauerite in the current Jasun auctions?)

16th Sep 2016 19:28 UTCDebbie Woolf Manager

There is no manganese sulphides at the Postmasburg manganese field, locentry updated and photos changed to bixbyite.

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