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 Post subject: phosphosiderite - cutting, locality, treatment???
PostPosted: Mon Jan 14, 2013 7:22 pm 
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Anybody importing or cutting phosphosiderite, a cabbing material, supposedly from somewhere in Chile?

It's a beautiful stone, and yet I still cannot find the exact locality, nor whether it is genuinely untreated, via heat or resin impregnation.

Anybody with firsthand experience, that's either cutting it or importing it to the US, would really make my day if any info could be supplied.

There's a lot of interest over at MinDat as well; finding multi-kilo sized masses, solid and cuttable, is really bizarre for this mineral.

I'd love to get a piece analyzed.

Thanks a ton for any detailed info!


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Mon Jan 14, 2013 7:30 pm 
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We discussed it in another thread
http://www.gemologyonline.com/Forum/php ... =6&t=13689

As mentioned on that thread, it is a curiosity more than a contender as a gem variety. :)


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Mon Jan 14, 2013 10:54 pm 
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Because of cleavage and low hardness? That definitely tends to be much better tolerated in cabochon material than facet material--just look at seraphinite.


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Tue Jan 15, 2013 12:13 pm 
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OK.....I can't tell if you are joking.
Again, please correct me if I am wrong, but seraphinite (clinochlore) is another collectible curiosity, used predominately for carving and decoration. The hardness as I understand it 2-4.

Varieties of calcite, like "Mexican onyx" have been used as decorative objects for centuries, as have varieties of serpentine, soapstone, etc. Would we call these "gem" varieties?

I guess it's debatable. :|


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Tue Jan 15, 2013 5:29 pm 
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I've seen quite a few cabochons of Seraphinite, some even set in pendants. I've seen similar things with beautifully calcified fossils (eg: cabochons cut from cross-sections of baculites replaced with golden calcite). Seraphinite is kinda on the cutting edge of ridiculous, hardness-wise (and from what I hear, a real pain to cut), but cut stones are beautiful enough that it apparently still sells.


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Tue Jan 15, 2013 10:25 pm 
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There are different markets for a huge range of cutting materials. Take a long look through Etsy to see the various stones that are utilized for use in handcrafted jewelry. I'm currently learning the tricks of cutting and polishing seraphinite - it yields interesting finished stones.

It's a fascinating mineral with an unique appearance and should be fine (with care) in a pendant or earrings. It's not a lot softer than many other stones that are widely used in (mostly silver) jewelry like azurite, malachite, amber, coral and many others. It's very popular as a "gem show" specialty in the U.S.

Getting back to the phosphosiderite issue, there's no doubt it's being treated to improve hardness (and possibly color). One of the main marketers of beads and (presumably) rough is Colbaugh Processing Inc., an AZ firm specializing in gemstone treatments (turquoise, rainbow calsilica, etc.) The rough phosphosiderite I've found on line is clearly identified as being treated.

As for the source, I have a hunch it's either Peru or Chile. The owner of Nuevo Mundo Imports http://www.nuevomundoimports.net/contact-us.html posted an image on another forum of a huge amount of the material being readied for shipment. I think an email to him could unravel many of Icehut's questions. He is also a member of G.O.

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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Tue Jan 15, 2013 10:58 pm 
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Fair enough.....you're changing my mind.


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Wed Jan 16, 2013 1:46 pm 
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Getting back to the phosphosiderite issue, there's no doubt it's being treated to improve hardness (and possibly color).


Definetely. Containing water phosphosiderite has some Raman peaks between 3000 and 3500 cm-1. A sample we recently analysed however exhibited typical Opticon or similar type epoxy resin peaks between 2800 and 3100 cm-1. Green line is the sample, a mixture of phosphosiderite and epoxy peaks.

Image

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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Fri Feb 08, 2013 3:25 pm 
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So a few notes on my experience with this material:

1) it does come from Chile. I don't really have a more precise locality, though. Quite a bit of Chilean material actually goes through Lima, probably because there is a more established network of dealers/resellers. I have not checked in to see if production is still ongoing. I know it is seasonal, due to snowfall in the austral winter.

2) phosphosiderite varies in density and hardness along a spectrum that is comparable to turquoise. Low grade stuff is quite chalky, powdery, and light, with low color saturation. Really high grade stuff can be cut without treatment, just like really high grade natural turquoise, but it is scarce in that quality.

That said, most of the stuff on the US market is treated, I believe. I have a bit of natural material I can send out if someone wants to do some spectroscopy on non-treated material. I've thought about doing some stabilization myself but never got around to it.

Any other questions just ask, I will do my best to answer...


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 Post subject: Re: phosphosiderite - cutting, locality, treatment???
PostPosted: Mon Feb 11, 2013 7:59 pm 
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Good day folks. I have been cabbing some seraphinite, I really like the colors and patterns. It cuts really easy using 600 for shaping and 1200 for polish...I have yet to achieve a true mirror polish, but have gotten closer with 3000 diamond on a balloon buff. I have found that it will present soft spots and cracks which will bloom into craters. But the worst thing I did was dop some with epoxy...needless to say those pieces broke up. It does seem to dop well with green wax. All in all, I like it.

ken


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