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Identity HelpMasuyite?

13th Aug 2015 23:15 UTCFlorian Baur

I have a Shinkolobwe specimen which according to the Christophe Dubois label has Masuyite, Bequerelite and Curite crystals.

The attached photo shows the alledged Masuyite as the small red tufts in the background. FOV is 20 mm. The reason I started to wonder if this really is Masuyite is that I couldn't find any photos of Masuyite needles. Curite however often occurs as needles, though it's usually more yellow or orange-red. Unfortunately both Curite and Masuyite are lead uranyl hydroxides, the former with a lead:uranium ratio of 3:8 the latter of 3:9 so single crystal XRD would probably be the only sure way to know?

All those Shinkolobwe U-minerals are hard to tell apart. I saw a photo of a Masuyite that to me looks exactly like Billietite does on other photos ...

14th Aug 2015 02:58 UTCDoug Daniels

Well, give them time....the lead:uranium ratios will change, so you'll have a new naming dillema.....(OK, a LOT of time)

14th Aug 2015 09:29 UTCFlorian Baur

If it was just the name, but Masuyite is much rarer, so to the determined collector this is an important issue! ;)

14th Aug 2015 11:42 UTCPaul De Bondt Manager

Florian,

Personally, I never saw masuyite in needle either.

You can not distinguish the members of this group by color.

Some say the one is reddisher than the other but I saw different shades in color on analysed specimens.

The only thing you can do is an EDX and Raman to identifie the mineral. It will cost you a little but you will have a mineral specimen instead of a name on a lable with a ???????. :-D

If it's not the mineral on the label, you may ask the dealer a refund, if you can prove it.

I hope this helps.

Best regards from Belgium.

Paul.

16th Aug 2015 22:23 UTCFlorian Baur

Fortunately we can do EDX now ourselves, but do you think it's possible to distinguish between the two?

Masuyite is 6.7% U, 20% Pb, 73% O (atomic-%)

Curite is 7.3% U, 19.5% Pb, 73.2% O

I have no experience in EDX but I think such minor differences are hard to tell?

The thing is, the previous collectors label (not the dealer) states Masuyite AND Curite. I wonder if maybe he meant he wasn't sure. On another specimen from the same dealer and same ex collection a very similar looking red mineral is labeled Curite... Anyway, the specimen is quite nice regardless of whether it being Masuyite or Curite, it's quite pure Uraninite matrix with lots of little cubes, some coated by secondaries and has nice Becquerelite shards - at least those seem to be real. ;) Still, Masuyite certainly fetches a higher price.

I never did Raman and we don't have one, but isn't a larger amount of sample required? I know some people who could do single crystal XRD, that's probably the only way?

16th Aug 2015 23:17 UTCAlfredo Petrov Manager

EDX would be quite useless in this case and, as Paul pointed out, colour is not definitive either. I'm not sure about Raman... might work? If not, then XRD.

17th Aug 2015 13:05 UTCUwe Kolitsch Manager

"I never did Raman and we don't have one, but isn't a larger amount of sample required?"

No; since the spot size is only 1-2 micron, a sample need only be larger/thicker than about 4-10 micron (depending on how deep the laser penetrates into the sample.

17th Aug 2015 18:35 UTCFlorian Baur

Uwe, good to know. There once was a discussion on getting a Raman, maybe I can rekindle it for my own purposes... ;)

I'd rather do this in-house as I learned that even most chemists react somewhat strange when it comes to Uranium and we don't have a single crystal XRD.

The dealer/collector from whom the label comes is Christophe Dubois, apparently a french collector. I didn't know him so I don't know his expertise on U-minerals/Shinkolobwe. I saw he'll be in Munich this so maybe I'll just try and ask him.

17th Aug 2015 20:50 UTCTravis Olds Expert

Florian,

I'm a Ph.D. student at a U-friendly lab at Notre Dame (in fact we primarily use U) and would be happy to try single xl XRD. Looks like there are plenty of xls there to try, so scrape from a location that won't cause too much damage and stick them in a vial and send me a email if/when you're ready to ship: tolds@nd.edu. I would only need a few xls.

Assuming they diffract well I can collect enough data to give a unit cell in ~15 minutes. Feel free to include anything else on there that looks strange, I think there are plenty more U-phases from Shinkolobwe that could be brand new. We have a Raman but I doubt there will be much difference in the bands between the two. There's no better way to tell what phase you have than knowing the crystal structure!

Travis

17th Aug 2015 21:22 UTCTravis Olds Expert

Florian,

This is entirely unrelated (so I apologize for hijacking your thread) but I just saw the pictures of your radian barytes on your page--did a little creeping, ha. :)-D I've been trying to get a hold of a sample for a long while. Any chance you have one other for trade? I have some rare African U-phases you might be interested in, and/or some of the newly named U-sulfates coming out of Red Canyon in Utah (belakovskiite, bluelizardite, plasilite, etc.).

Travis

17th Aug 2015 21:41 UTCFlorian Baur

Travis, dropped you a PM (but in case anyone wonders, I just have this one Radian Baryte).

17th Aug 2015 21:48 UTCTravis Olds Expert

Florian,

Ah, okay the search continues. No worries. No sign of the PM yet, but will give it a while.

Travis

17th Aug 2015 22:13 UTCTravis Olds Expert

Florian, again, I'd be happy to try single Xl XRD on your presumed masuyite. I think my original post was lost in the flurry of messages.

28th Aug 2015 15:29 UTCFlorian Baur

Travis, that's a great offer, I only found it just now. I will try to harvest two or three good crystals and get back to you.

In return if you ever need something EDX'ed, let me know. Also, our specialty is luminescence, like emission/excitation, decay times, low temperature measurements and so on.

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