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Unknown black mineral from Brazil

Posted by Mark Van Tomme

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Mark Van Tomme

Unknown black mineral from Brazil
August 04, 2012 09:46PM

Registered: 6 years ago
Posts: 19

Hi everyone,

I've just received this sample as a gift from and old lady, according to her, her brother used to work in a mine in the state of Goiás.

For the moment I'm unable to make any tests, I'm at a hotel..

I believe Schorl can be excluded.

I hope the pictures are ok,

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open | download - Pic 3.jpg (538.4 KB)

Emil Box

Re: Unknown black mineral from Brazil
August 04, 2012 10:21PM

Registered: 4 years ago
Posts: 136

Hi Mark,

it looks like ferberite perhaps from Mangabeira. 'Wolframite' is a groupe name, should be in''.

Greetings
Milo.

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Mark Van Tomme

Re: Unknown black mineral from Brazil
August 05, 2012 12:39PM

Registered: 6 years ago
Posts: 19

Thanks Milo! smiling smiley

I tried to scratch another sample with a knife to no avail.

I would say its luster is metallic to sub-metallic.

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Mark Van Tomme

Re: Unknown black mineral from Brazil
August 05, 2012 12:40PM

Registered: 6 years ago
Posts: 19

Just to add that I tried to make additional pics under sunlight but they all came out of focus..

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Luiz Alberto Dias Menezes, Fo.

Re: Unknown black mineral from Brazil
August 07, 2012 02:43AM

Registered: 4 years ago
Posts: 300

It is very hard to identify, just by a photo, a dark brown to black mineral that do no show a crystal shape; it can be wolframite, but cassiterite would be another possibility; by handling it we would have a feeling about the density.

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Tim Jokela Jr

Re: Unknown black mineral from Brazil
August 07, 2012 01:14PM

Registered: 7 years ago
Posts: 774

I'd suggest tantalite / columbite groups.

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Peter Haas

Re: Unknown black mineral from Brazil
August 07, 2012 08:25PM

Registered: 7 years ago
Posts: 3,762

The bright silvery fracture (first picture) excludes cassiterite and wolframite.

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