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Identity Helpstannite or tetrahedrite?

27th Apr 2012 00:45 UTCReiner Mielke Expert

This specimen is from Bolivia, can anyone tell me which one it is based on these photos? Associated minerals are quartz,pyrite, wavellite? and orpiment?

27th Apr 2012 04:02 UTCFrank Keutsch Expert

Do you have locality information?

Orpiment is quite rare in Bolivia. The piece could be from Siglo XX. To me it looks more like stannite, but hard to tell...

27th Apr 2012 12:01 UTCAlfredo Petrov Manager

Several years (12?) ago, there was a one-time find of a big pocket of stannite crystal crusts with white wavellite balls in the Cerro Rico, Potosi. These usually had some arsenopyrite with them too. Do you see any arsenopyrite on yours, Reiner?

As Frank said, orpiment would be very unusual for Bolivia. I can't recall ever seeing any at all.

27th Apr 2012 13:46 UTCFrank Keutsch Expert

Reiner, can you show a photograph of the whole specimen as it might be easier to say something about the locality...

Frank

29th Apr 2012 17:13 UTCMaggie Wilson Expert

Taking a break from weeding the gardens...

The stannite specimen is from the San Jose Mine, Oruro, Bolivia - here are several shots that show the matrix.

30th Apr 2012 00:15 UTCReiner Mielke Expert

There is no arsenopyrite on the specimen. Attached is a photo of a small ( 0.5mm) striated crystal sticking out of a stannite xl that is covered in what I thought was orpiment, could be something else. All I know is that it is not a carbonate and is soft. Don't know what the crystal is that it is coating, any thoughts on that?

30th Apr 2012 00:21 UTCAlfredo Petrov Manager

Yes, looking at the whole specimen, it does indeed look like San Jose stannite. The white material is probably alunite or natroalunite rather than wavellite. The small striated crystal sticking out of the stannite is probably andorite. Need a closer photo of the orange crust.

30th Apr 2012 02:01 UTCReiner Mielke Expert

Thank you Alfredo.