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Techniques for CollectorsEDS question

3rd May 2017 19:13 UTCJennifer Cindrich

I sent a calcite specimen to kerry day for analysis it also included another mineral suspected by kerry as Aragonite. if the EDS cannot distinguish between the two what are the other possibilities that the Aragonite would be ?

3rd May 2017 20:01 UTCGünter Frenz Expert

Calcite and Aragonite can easily be distinguished with Raman-spectroscopy.

Günter

3rd May 2017 20:10 UTCJennifer Cindrich

-- moved topic --

4th May 2017 01:22 UTCReiner Mielke Expert

See: https://www.mindat.org/forum.php?read,100,179708,page=1

4th May 2017 06:10 UTCJoel Dyer

Hi Jennifer,

Both Günter and Reiner give a good answer. Without the need to use any chemicals or "complicated" processes, by far Raman analysis is the quickest and simplest for solving this particular kind of matter.

Cheers,

Joel

4th May 2017 12:19 UTCJennifer Cindrich

Thanks to you all!

4th May 2017 13:27 UTCŁukasz Kruszewski Expert

The best and most cheap way is undoubtedly powder X-Ray diffraction (PXRD).

5th May 2017 01:48 UTCReiner Mielke Expert

Easy and cheap depend on whether or not you have the equipment and are able to run it yourself. The chemical method is truly easy and cheap because the cost of the chemicals are relatively cheap and anyone can do it and interpret the results. I made up a small batch (100ml) of Feigl's solution which is now 35 years old, and it still works!

5th May 2017 04:08 UTCDoug Daniels

Yes, Reiner, but how easy is it now for Joe Public to buy even small amounts of silver sulfate and manganese sulfate? And many other chemicals useful for identifying some of the common minerals? 35 years ago it was a bit easy.....nowadays, good luck!

5th May 2017 05:44 UTCJoel Dyer

Well, I know this thread is dragging on and Jennifer probably has decided on her method. However, I feel the (unhealthy?) urge to comment one more time.

In earlier times, I would probably have sent a piece of my own similar material to John (Attard) to analyse :-) . No doubt, I'll use John's service again in the near future, when the occasion arises & I get together some extra money.

...

Doug is right about chemicals: in Finland, too, it is getting harder and harder to get hold of many commonplace, really not that dangerous chemicals. I've ran into many problems over here myself.

And ordering some stuff via Ebay might land me in trouble with the Customs, so it's not worth the risk, as I have my 2 company's reputations to think about, too...Many housing rules prohibit the storing of chemicals on premise, anyways.

Some of the stuff that have been mentioned (HF acid, concentrated other acids etc) in the message threads are positively dangerous, or not suitable for people who are not well used to handling chemicals and who might not have previous good knowledge of chemical reactions. Notwithstanding, for the right people living in the right locations, Reiner's solution is perfect.

...

Łukasz, I was slightly bothered about your comment, alhough I have an immense respect for your knowledge and experience.

Reiner's counter-comment is in place, I think, and is equally valid for my own earlier suggestions as well.

But mainly, I was thinking of the destructive quality of XRD. I once got sent a sample or two of some rare stuff sent to analysis: half of it was sacrificed to EDS (didn't get the remains back), and half to XRD. In the end, I got no answer and I'm now left with no material for myself :-( .

I've several times myself in Finland - cheaply and quickly - analyzed for others gemstones, very small crystals and semi-amorphous material that could not be determined with EDS properly, and that were not permitted to be damaged in any way.

In non-destructive methods like Raman / FTIR. you need equally small amounts, but the valuable sample is not damaged. So, why can't we keep options open in all directions. Note: I'm not offering to help anyone here, so please, don't construe my words as an "advertisement" for any particular method. I would also agree that very often XRD is the best option, case closed.

And about cheap & not cheap: here in Finland the only private company I personally know for XRD / EDS work charges about 100€ / either method. For EDS; carbon coating and preparation is extra on top of that. The Geological Survey has told me that any analysis work costs a minimum of 200€ and that does not include any extra work ( micro/macro photography, detailed intepretation etc). So, basically, the only option here usually is to send stuff abroad (Kerry, Attard), or try to get someone to pulls strings abroad with research scientists who are already up to their necks in academic work :-) .

Cheers,

Joel

5th May 2017 15:52 UTCŁukasz Kruszewski Expert

I assume the Feigl's solution can help in discriminating calcite and aragonite... but what if you have vaterite and/or ikaite? PXRD is there a must, although EBSD may be used, which is however much more expensive.

5th May 2017 15:52 UTCŁukasz Kruszewski Expert

Well, then it is good to find a scientist to cooperate (-;

6th May 2017 00:36 UTCAlfredo Petrov Manager

But unless you live in a very very cold place (like Antarctica or northern Greenland), you won't have any ikaite in your collection to analyze. ;))

6th May 2017 22:05 UTCJennifer Cindrich

vaterite.... i hope its vaterite

6th May 2017 22:06 UTCJennifer Cindrich

nope- pretty hot here in texas

6th May 2017 23:31 UTCReiner Mielke Expert

I have no idea if the Feigl test can distinguish valerite from aragonite, which raises an interesting question. Is valerite very rare or has it just not been recognized for a lack of testing? You can probably say that about a lot of rare white minerals not to mention other ordinary colored minerals.

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