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Identity HelpIs this Arsenocrandallite??????

12th Sep 2010 18:39 UTCGeorge Eric Stanley Curtis

Hi all,

This was found at Wheal Unity (Poldice) in Cornwall UK in a hole someone else had dug.

It is inside a large and heavy chunk of Arsenopyrite, lining all the holes and cavities.

It is transparent with a hint of blue, with a 'wet' look, even when clean and dry.

It has a hardness of about 5, is not affected by HCl.

It does nothing under UV (lw or sw) and there is no detectable radioactivity.

In my own efforts it appears to be Arsenocrandallite, but that is little more than a guess.

Can anyone help? Is there anything else it could be?

Thanks in advance,

Eric

12th Sep 2010 19:00 UTCRonald John Gyllenhammer Expert

Maybe Arsenogorceixite.

12th Sep 2010 19:17 UTCSteve Rust Manager

The only way to tell is by xrd, edx.

12th Sep 2010 20:13 UTCGeorge Eric Stanley Curtis

Hi

I know arsenogorceixite and arsenocrandallie are very similar to look at, judging by the pics on mindat, and are in the same subgroup, but the data says that arsenogorceixite is hardness 4, my sample appears to be harder, about 5+, which is the figure (5.5) given by the data for arsenocrandallite.

I will recheck the hardness with greater care.

Thanks for the advice

Eric

12th Sep 2010 21:13 UTCUwe Kolitsch Manager

I concur that XRD and/or EDS will be necessary (this may also be secondary globular apatite, or allophane? - not familiar with the locality though).

13th Sep 2010 11:57 UTCGeorge Eric Stanley Curtis

Uwe, the locality is rich in arsenates like Olivenite, and the material is in, and directly on, a matrix of arsenopyrite.

XRD/EDS would be nice but I prefer to exhaust all other means first, since I do not know of any local commercial labs that provide such a service.

Thanks,

Eric B)