FMF - Friends of Minerals Forum, discussion and message board

[Gerhard Niklasch]

Debbie seems to be on to something here...

Hematite isn't tetragonal, and the angles and surface texture look wrong for Hausmannite.

But Braunite might fit, and similar-looking material from the Kalahari Manganese Fields (Wessels, N'Chwaning...) is found in the mindat gallery:
https://www.mindat.org/gallery.php?loc=14466&min=757

This is not to say that good crystals on a matrix of what seems to be more of the same material in massive form would necessarily have to come from there, of course! So just another guess. (Associated garnets would be plausible, though.)

Have you checked the hardness, and could you try to measure the density? What about streak (using a not so showy corner of the specimen)?

Cheers, Gerhard

[Debbie Woolf]

I think Gerhard is onto something here too ... :0)

I'm no expert but have an interest in minerals from this region it's not Hausmannite but Braunite II is quite likely, the streak test will determine this, Braunite is black & Hematite is red.
In 1995 Braunite II was found up to 3cm from Wessel mine associated with Andradite, Hausmannite & Ettringite (Bruce Cairncross - The Manganese Adventure).

[Pete Richards]

Somehow I missed this thread when it came through 9 months ago!

This certainly looks like hematite from N'Chwaning (#2) to me.

Tobi, please look down on the top of that most prominent crystal and see if it has four-fold or six- (or three-) fold symmetry. If the latter, I vote for hematite from N'Chwaning.

On quick reading of this thread, it seems everybody (but, near the end, Jordi) went along with your initial assumption of anatase, and therefore four-fold symmetry. That may be a fatal error of thinking....

[Tobi]

- The streak isn't black, but rather a slightly reddish brown.

- Hardness seems to be the same as hematite: Using an Elba hematite for hardness test showed that both specimens do not scratch each other in any way. (And braunite should slightly scratch hematite).

- The crystal symmetry is not good to diagnose, for no crystal is complete all around.

According to the results i would guess it is hematite (same hardness, reddish and not black streak) from a mine in South Africa.

[Riccardo Modanesi]

HI to everybody! Yes, fully agree: it looks like an hematite. I don't know whether from the Elba Isle or from another locality, but the rust-red oxydation is very easy to be noticed. However defitely not an anatase or arsenopyrite. Now it's my time to say: forget these adventures!
Greetings from Italy by Riccardo.

[Tobi]

Yes, hematite for sure. But not from Elba. I've seen thousands of Elba hematites, none of them looked like that. This habitus is typically Kalahari Manganese Fields localities like Wessels Mine or N'Chwaning Mines ...