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Fakes & Fraudsphosphosiderite cabochons

9th Mar 2010 05:23 UTCRick Dalrymple Expert

I have seen a lot of this stuff on the market lately mostly labeled from Brazil.

http://www.mineralauctions.com/auctions/gemstone-consignment-auction-210-225/phosphosiderite-great-color-12671.html

I know it use to be made from variscite from Lucin, Utah. I have even made some of it myself, bit it has never come out as evenly colored as some of the material from Brazil. It is also disturbing that it is never disclosed that it is completely heat treated.

Does anyone know exactly how to make it turn purple so that the color is so even?

Edit: (spelling)

9th Mar 2010 13:39 UTCAlfredo Petrov Manager

" It is also disturbing that it is never disclosed that it is completely heat treated."

What makes you think it is heat treated? Is there evidence, or just malicious rumor? I would think you couldn't heat treat iron phosphates; they'd turn brown, dark red or black.

(I have no idea whether these violet cabochons are natural phosphosiderite or not - can't tell just by looking at a picture - but I tend to give sellers the benefit of the doubt unless there is some specific reason to think fraud.)

9th Mar 2010 18:28 UTCRick Dalrymple Expert

Alfredo,

I first saw these in a jewelry store in southern Utah ( about 5 or 6 years ago) being sold as Utahs Most Unique Gemstone and asked where it came from, being from Utah and a Utah collector. The guy that owned the store told me you just take Lucin, variscite and bake it in a kiln and after a set amount of time you get this beautiful pink phosphosiderite.

Being an experimentallist, I couldn't wait to get home and try it. Sure enough, I cooked probably 20 pounds of variscite experimenting and got it to turn from green to pink around the edges. Just not that consistant pink.

I tried cooking it with a torch and got a more darker lavander. It took about 25 minutes at cherry red before it started to turn.

I have looked long and hard to find this kind of materail in the rough. It is never sold in the rough, only as finished cabs, which makes me think that it is not naturally found that way. Mine turned out very grainy after cooking and all the materail I have always seen for sale seems to be grainy leading me to think all of it has been cooked and then sealed with some kind of stone sealer or epoxy, usually opticon.

Don't think I have anything against a particular dealer. I have purchased from him in the past and will do so again in the future.

9th Mar 2010 19:07 UTCAlfredo Petrov Manager

Thanks, Rick.

I guess the first step would be to get one of these cabs and check whether it's really phosphosiderite or not. If it turns out to be really Al-phosphate, with minor Fe, then it can't be phosphosiderite, and then likely either cooked Utah variscite or something synthetic. If it is really phosphosiderite as advertized, then I'd suspect some as yet unknown Brazil source for massive material - The colour is right.

9th Mar 2010 19:45 UTCRick Dalrymple Expert

-- moved topic --

9th Mar 2010 19:55 UTCRick Dalrymple Expert

Alfredo,

That's a good idea. I should have some analysed but that is beyond my capability right now.

I find it hard to believe that there would be some secret location that no one knows about except a few people who are selling the cabs. They are beautiful in color and I would suspect they would be in high demand with jewelers. If there was only one secret spot I would figure the price to be considerably more. Just a rambling thought.

9th Mar 2010 20:12 UTCAlfredo Petrov Manager

You may well be right, it is a bit suspicious, although gem producers do tend to be secretive about new sources. Ametrine was produced in tons, for more than a decade, before we found out where it was really coming from, and initially some people thought it might be synthetic. Anyone in the gem business could provide similar examples.

9th Mar 2010 20:49 UTCSteve Hardinger 🌟 Expert

The owner of the url given at the start of this thread is very well respected. I value his opinion, and I'd like to hear his input.

9th Mar 2010 21:43 UTCHenry Barwood

Just a couple of comments. If you are heating variscite to a "red heat", you no longer have variscite. Variscite will dehydrate at something like 300 oC. The material called "redondite", an aluminan strengite, used to be heat treated to make it plant available when used as a fertilizer. Variscite, being an aluminum phosphate would never turn into phosphosiderite spontaneously, no matter how much you heated it. I used to synthesize massive microcrystalline phosphosiderite for phosphorus avaiability studies. Perhaps this new stuff is actually synthetic?

9th Mar 2010 21:48 UTCRick Dalrymple Expert

Henry,

By what you are saying I was creating rodondite and not phosphosiderite?

9th Mar 2010 21:51 UTCRick Dalrymple Expert

Steve,

I am not calling into question his reputation. It would be foolish to think he doesn't know what he is doing. But, as a mineral dealer myself, I also know it is impossible to know everything. I have made mistakes in the past as I am sure every mineral dealer and collector has. I am just calling into question the validity of this one item. I have been suspicious of it since I first saw it 5 or 6 years ago. I purchased it in an attempt to figure out what it was. I have not seen any of it on the market since then, until recently. Now I have seen it several times and always listed from a different place.

Like I said before, I was able to get some results in making it from variscite. I personnally think it is manufactured.

9th Mar 2010 23:41 UTCSteve Hardinger 🌟 Expert

Rick, I wasn't questioning you. Instead I was inviting the owner of the specimen used as an example to comment. The specimen's owner informs me that he is investigating.

10th Mar 2010 00:30 UTCRick Dalrymple Expert

Steve,

No problem. I didn't really mean to stir up a big deal with this. I was hoping to find more information about how the process works for "baking" variscite into what they are calling phosphosiderite. My own experiments were not as successful as I had hoped. And as Henry pointed out I wasn't even converting variscite to phosphosiderite, it was redondite.

It seams I can always find someone on Mindat that can answer my questions about such things.

10th Mar 2010 03:29 UTCRobert Lavinsky Expert

thanks to Steve Hardinger for telling me of this thread. seems to hav etrickled into my consigned gems from a reliable source , and we have pulled it for sale based on this. sure wish somebody had bothered to email us first to ask....

10th Mar 2010 03:45 UTCHenry Barwood

Hi Rick,

Actually "redondite" is strengite with a small aluminum content. It was from guano deposits on the island of Redondo in the Carribean. The Utah variscite, at least those I've analyzed, were all either variscite or crandallite.

I'm not saying that is a synthetic, just that it is very easy to precipitate phosphosiderite and turquoise powder. A little pressure and some epoxy and you have beautiful cutting material.

Henry

10th Mar 2010 04:50 UTCRick Dalrymple Expert

Rob,

I apologize for any hassle this has caused you. I have nothing but the utmost respect for you. I enjoy your actions, even though I don't seam to be able to win to many of them.

I was not trying to say it should or should not be sold. I was just inquiring as to how it was produced. It is a unique colored gem material that makes beautiful jewelry in both silver and gold.

Henry,

How did you go about go about dehydrating the variscite? How long at what temperature did you use?

Once again, I was not trying to point a finger at anyone for anything.

10th Mar 2010 13:39 UTCHenry Barwood

Rick,

I used to run a lot of thermogravimetric analyses. The technique can be used to determine the LOI and the thermal characteristics of a sample. Hydrated phosphates have different thermal curves that allow you to identify, and in many cases, quantify them. You have to be a bit careful with materials that contain Fe2+ because it will oxidize and cause a weight gain.

7th Dec 2010 21:17 UTCNuevo Mundo

I hate to resurrect a dormant topic, but I think I should add my two cents.

I have had the opportunity to see for myself a good quantity of phosphosiderite rough. The material I saw was NOT stabilized or treated in any way, and the rough was mostly nodules that looked convincingly natural. i saw pieces or rough from under 2" to over 2' in diameter, and there was nothing to indicate that they were artificial or treated in any respect.

I think I have a photo of a few dozen kilos of untreated rough. If there is interest I will search for it when I get back to my home computer and post it here.

8th Dec 2010 02:39 UTCRick Dalrymple Expert

Arron,

Thanks for your information. I appreciate the eye witness account. I would love to see the photos of the rough and where I can purchase some.

I was originally told by a local jeweler they baked the variscite from Lucin, Utah to turn it into phosphosiderite. I used a torch to heat it to cherry red for over 30 minutes and was able to get a violet color not quite the same as the phosphosiderite cabs. So I assumed they had a better process than I did.

This jeweler insisted this was a Utah material. I see now that it was just for my benefit.

8th Dec 2010 03:58 UTCNuevo Mundo

Here is a pic of ~100 kilos of untreated rough. The huge piece on the left is apparently one of the largest to come out...

I don't think there is any way pieces of that size could be effectively heat treated.

8th Dec 2010 04:11 UTCAlfredo Petrov Manager

Aaron wrote: I don't think there is any way pieces of that size could be effectively heat treated.

I'm not saying they're heat treated, but I'm curious why size would indicate anything about the likelihood of such heat treatment? if I wanted to experiment with heat treatments, I'm sure my friendly local brick factory or ceramic artist would let me put pieces much bigger than that into their ovens for a day or several days, and see what comes out.

8th Dec 2010 04:26 UTCHenry Barwood

Aaron,

Is there a locality associated with this material?

8th Dec 2010 04:32 UTCNuevo Mundo

That is a good point, Alfredo. I was just thinking back on my own difficulties in trying to enhance the color in Fe bearing agates, but there are surely folks out there who are much better and better equipped than I.

I still think that heat treating things with so much variation in shape and size would not be easy.

8th Dec 2010 04:36 UTCNuevo Mundo

Henry,

The most precise locality I could get was that it comes from 'Chile'. It is perfectly possible that it is in fact from Chile, but I think it is also possible that the actual origin is somewhere in Bolivia or Peru. As with any new material, no one wants to give me any details...

9th Dec 2010 02:36 UTCLuiz Alberto Dias Menezes, Fo.

What I can say is that if the 100 kg of the gem rough shown on Aaron's photo is really phosphosiderite (what is impossible to me to say only by the photo), and if it really came from Brazil, the locality is not the Sapucaia pegmatite, Galiléia, Minas Gerais; I have collected minerals there for a long time and I have never seen anything similar; that pegmatite is located on the southern edge of the Sapucaia do Norte district, Galiléia, and indide this district there are more than 10 actively mined pegmatites, like the Boca Rica mine (where I have also never found anything similar); it is possible that any of them could have produced rough phosphosiderite and the name of the place was simplified from Sapucaia do Norte to just Sapucaia.

It is very hard to identify phosphosiderite without any analysis; Aaron, have you had your rough material X-rayed?

9th Dec 2010 03:26 UTCNuevo Mundo

No, I have not had any sort of analysis done on this material. All I can say with any certainty is that this is the same material being sold in cabs and beads as phosphosiderite.

13th Dec 2010 19:31 UTCMichael Hatskel

Purple-red colors of the phosphosiderite, strengite and variscite found in Brazilian material from Sapucaia is a challenge to discern because they are so close sometimes. The phosphosiderite at least has a "decency" of occurring in smooth globules, not crystalline globules like that other two, so it could be easier identified. B)

Dana 7th Ed. says "On slight heating the color of green variscite may become lavender to purplish-red" and makes a reference to the 1912 publications by Schaller (see pp. 759 and 761 in Vol. 2).

It doesn't mean, of course, that it turns into phosphosiderite, because Al is not going anywhere upon heating. But it seems that some Fe shall be present to get such a color.

Also, some of the chemical compositions provided by Dana show minor Cr (e.g. 0.18% Cr2O3 for the Lucin variscite). Could that be enough for the Cr to contribute as a purple-pink chromophore?

Not sure what is the actual temperature of the "slight heating" - below the dehydration point or above it.

19th Dec 2010 16:02 UTCRay Ladbury

FWIW, I have not seen this material in Brazil. I would have thought that it would be at the Teofilo Otoni show, and while I was not looking for it specifically, I would have thought it would catch my eye.

I do have samples of phosphosiderite associated with red variscite that I brought back from Brazil a few years ago. Both the variscite AND the phosphosiderite are in tiny crystals, and I haven't seen much larger for either species, even in high-end specimens.

Don't know if that helps, but that is what I know.

11th Jan 2013 20:42 UTCLyle Gordon

I'm a PhD student in Materials Science. I found this thread while searching for a phosphosiderite specimen. I need one for use as a reference material for some X-ray spectroscopy.

I was going to buy some cabochons on e-bay and do XRD. But, if someone has some I would be happy to grind up a coupld and do XRD and post the results and then use the powder for my experiments.

Thanks very much,

Lyle

11th Jan 2013 23:23 UTCRicardo Scholz

Hello Guys,

this phosphosiderite probably is from Copiapo, Chile.

Best wishes,

Ricardo

11th Jan 2013 23:56 UTCAlfredo Petrov Manager

I think only the marketers live there. The actual locality is pretty high in the Andes.

12th Jan 2013 01:42 UTCRick Dalrymple Expert

I haven't posted to this for a long time but I do read all the comments.

I am still waiting for a definitive answer and location;-)

Thanks all for your imput.

9th Feb 2013 18:27 UTCLyle Gordon

I needed some Phosphosiderite for a reference material for some X-ray spectroscopy work and I came across this thread in my search. I contacted Alfredo Petrov for a piece of phosphosiderite and I also purchased a cabochon on eBay (http://www.ebay.com/itm/PHOSPHOSIDERITE-Peru-10mm-Cabochon-1-/380504651033?pt=LH_DefaultDomain_0&hash=item5897d83519) since they were very inexpensive. I ground up both samples. I performed X-ray diffraction on both specimens and I can confirm that they are both phosphosiderite. I also performed Phosphorus K-edge XANES and Iron K-edge EXAFS on the cabochon. The P K-edge XANES matches well with published data (Ellery, D I et al, J Synchrotron Radiat. 2011 March 1; 18(Pt 2): 189–197). The EXAFS fit (dashed lines in the figures) match well to a phosphosiderite model derived from a published crystal structure (Moore P B, American Mineralogist 51 (1966) 168-176).

Here are the plots of the data for anyone that is interested:

https://dl.dropbox.com/u/3730003/phosphosiderite/XRD.png

https://dl.dropbox.com/u/3730003/phosphosiderite/PXANES.png

https://dl.dropbox.com/u/3730003/phosphosiderite/FeEXAFSk.png

https://dl.dropbox.com/u/3730003/phosphosiderite/FeEXAFSr.png

and here is the raw XRD data if anyone wants to play with it:

https://dl.dropbox.com/u/3730003/phosphosiderite/petrov%20phosphosiderite.txt

https://dl.dropbox.com/u/3730003/phosphosiderite/phosphosiderite%20cabochon.txt

9th Feb 2013 18:49 UTCLyle Gordon

Here is the Fe-K edge XANES plot that I forgot to include

https://dl.dropbox.com/u/3730003/phosphosiderite/FeXANES.png

9th Feb 2013 19:49 UTCTim Jokela Jr

Cool beans, Lyle. Appreciate the data.

18th Mar 2014 21:28 UTCNeil

Lyle,

I know it's a year later but I also have an interest in this material. I have a rough piece that I bought on eBay that looks like the rough photo posted above.

http://www.zbestvalue.com/images20/phosphosiderite1.jpg

Supposedly the material comes from Argentina or Chile but I can't confirm this. What I do know is that the specific gravity is incorrect for phosphosiderite. According to all the sources I can find on the internet the specific gravity should be 2.74-2.76. But I measured my sample multiple times and the specific gravity is 2.36.

Which is odd because this is closer to the specific gravity of variscite.

Could you do a specific gravity and refractive index measurement of your sample?

Neil

27th Nov 2014 23:52 UTCandres uteau

andres

NO SELLING ALLOWED !

Your messages have been removed.

Wayne Corwin

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