Thank you, this is great info. It’s very hard in that region to associate gemstones or beads with any specific culture beyond the neolithic (where there are some roughly distinct shell beads, I believe). It was a comparatively highly populated/settled region with tremendous change since the early Bronze Age. But the mineral characteristics of those sources are very intersting and helpful, thank you!
Thank you. I will also scout this forum
for labs that might be able to help at a reasonable cost.
I too will become the owner of these two books! thank you for the suggestion!
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Woah, amazing resources. Thank you!
Hello PaulB36648!
I haven’t been on this forum in a while and read with great interest this thread about your proposed research into turquoise jewelry (and other gems/minerals?) from ancient sources. I’m just a practical gemologist and gem cutter, so I’m not a lot of help in this matter myself. However, there is a lot of analysis of specimens that could be done, as Steve Hata points out. While tests are often destructive, some are not and others require only small samples. I think you need more input from some gemologists and geologists who are familiar with the testing procedures and the kinds of numbers you could get from them. If someone developed a database of the composition and appearance of found objects from various archaeological sites, it could become a great resource for researchers. I hope I am making sense here.
There is one fellow you should talk with, L. Bruce Jones. Bruce had an early and distinguished career in lab gemology before going into building same submarines. You can find him on Facebook. He knows all of the current sophisticated and expensive lab instruments and what kind of info can be gleaned from each of them. He can possibly assist you in determining what tests to use and what each will tell you.
If I were you I would also talk directly to GIA in Carlsbad. Their research journal is one of the main organs for research into gemstone parameters and their lab is one of the most sophisticated in the world. While they focus on gem ID and documenting new finds, I think they might find basic research into the gems of antiquity quite interesting. Possibly they would associate on some research project and even be able to suggest how to get funding.
Just throwing this out on the forum for public discussion. I’ll also try to DM you directly.
Hope this helps,
royjohn
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The use of a mass spectrometer present in some university laboratories and by measuring the ratio between stable and unstable isotopes can estimate the age of a rock or mineral, even a gem.
dr. Piero Manuelli FGA Gem-A
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Hello,
There is a facebook group “Lets Talk Quality Turquoise” that has members around the world, some sciency people and and some experts in turquoise. I think the ability to determine source of a stone requires in person examination, but the diagnostic criteria you are after might be the kinds of tests that GIA does.
Some people can determine where a stone is likely to have originated if its specific mines they are familiar with. But what smart gemologists will tell you is its not possible to do that in a picture. And turquoise experts will always offer an opinion with the caveat “only the miner knows where it truely came from”.
Try the FB group or the one on Turquoise Formation.
And if you have not discovered it yet, Mindat is a major database online of minerals and localities, sometimes with pictures of the localities & material, and good descriptive material.
P.S. I worked as an archaeologist early on in my career and was trying to do pottery origin analysis of meso american stuff based on the clay composition to map trade routes, so I appreciate the scope of your inquiry.
-tina
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Do you happen to have, or can point me to, a pic?
Thank you very much for the reply, it is great info. I’ll reach out to the contacts you suggest, thank you!
just the one I previously posted. I do not currently have any, although I do want to get some more when I find it!
laser ablation mass spect is only minimally destructive. However, unless university supported (grants) the cost of running a sample is prohibitive. I was quoted up to $6K per sample for whole rock analysis to do geochemistry, including isotopic analysis. That was just for the standard uranium//lead ratios, Sr/Rb and eNd ratios.
re mass spect: sampling both turquoise and matrix via laser ablation mass spect will give you a definitive answer as to the composition and source of the turquoise or any other stone… IF you can find a cross reference to same in the gemologic/mineralogic/geologic literature. Research Gate is where you can find all of this stuff, but you have to have had published a scientific paper to gain access. I had two publications that allowed me in.
Thanks, I missed this. Very helpful.
How far has your research into your fascinating and potentially ground breaking research gone so far?
I would suggest taking your samples to expert gemologists in turquoise first for visual inspection and nondestructive testing. You will need to get several opinions. I would be surprised if the opinions converged. Ultimately, the geologic origin and provenance can only be determined by trace element signatures and isotope ratios… the former can be obtained by electron microprobe which is very minimally destructive. the latter, by laser ablation mass spect… costly unless supported by grants. If you are doing this yourself, you need to approach academics. Someone should take interest. Full research projects have to be supported by grants. Getting grants without academic credentials is impossible.
Thanks for the encouraging note. I am currently working with some exceptional people who have helped a great deal. My biggest gap right now is with the geology/mineralogy. The help I need is quite specific, and it’s been a bit difficult to find the right person/people. An expert gemologist would also be very helpful on a number of levels, regardless of any possibility of definitively tracing specific gemstones to a singular point of origin. If you know of any, I’d be grateful for a referral. Thanks!
it depends on where you live. You could try and contact the turquoise museum in Albuquerque, NM… if you can’t go there in person they could have you ship it there for examination. [
The Turquoise Museum
[image]
The Turquoise Museum
https://turquoisemuseum.com
](https://turquoisemuseum.com/)
Turquoise Museum · Home · Joe Dan’s Corner · History and Mission
Note that this a commercial outfit… you will get charged a fee.
If you are anywhere near a university with a geology department, start there also. You might find someone who can refer you on. Another option is starting at a local jewerlry store. The proprietor may have ideas as where you can send your material for the kind of examination you are looking for.
Determining provenance will require analytic methods. You mentioned that you have to find specific help. What specific help is it? Please throw it out to the group and see if anyone can send you in the right direction.
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The technique that is now being intensively investigated for provenance ie origin of gems is Laser -Inductively Coupled Mass Spectroscopy or LA-ICPMS, where a laser is used to vaporise a very small area and the elemental isotopes in the vapour are analysed by a mass spectrometer and associated computer help. This usually gives a mass of mass data ie a geochemical fingerprint of the small sample analysed, often in terms of 20 significant elements/impurities. This technique has proven successful for me in fingerprinting zircon from the Mud Tank field in central Australia. There are however several caveats. One is in having enough representative samples and also previous LA-ICPMS data on distinct regions’ material. The second is the cost of analysis if a sufficiently robust data set is not available. Clearly, the technique could be used to trace turquoise origins similarly to sapphire and zircon if there are sufficient verified geographic samples available.
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I am well aware of Laser ablation inductively coupled plasma mass spect…Several presentations by GIA post docs at the Honolulu Goldschmidt geochemical society meeting used mass spec to determine the provenance of a mixed bag of colored stones. trace element signatures and isotope ratios were able to determine provenance to a specific area and sometimes to a specific mine. However the cost of running LA-ICPMS on a single sample is expensive… running multiple samples to generate a data set with variances is cost prohibitive unless one is a grad student, post doc or academic doing university sponsored research with grants. At least 20 samples from the same source area have to be analyzed to generate a meaningful data set… trace element (TE) ratios versus TE ratios and isotope/isotope ratios versus isotope/isotope ratios require enough samples to determine clustering and variance there of… I am well aware that these machines can cost up to a million and up to 50K per year for maintenance and technical support to run them…unless done at an institution under grants for research, costs are far too high for a private person to pay for out of pocket. Commercial labs charge an average of $200 per sample, less for academic institutions. Academic institutions charge less than commercial but often will not take samples due to busy time with their own demand. This method is still the most sensitive and accurate way to get geochemical data. EMP is cheaper but requires thin section sample preparation, increasing costs, doesn’t give as much data as LA ICP MS…Machines are getting cheaper, with some in the 100K range. However labor costs for prep time and run time remain high… around $50 per hour… accounting for the bulk of the cost for running a sample. I’m not aware that this technique has been used for turquoise or other copper minerals. Turquoise locales are diverse and numerous. Provenance data is lacking. The only studies that I know of are done by mining companies on bulk rock to explore for copper. Collecting of turquoise from copper mines, by employed miners, is highly discouraged by companies as it slows down earth moving operations. Turquoise along with everything else copper is stripped mined in bulk and sent to processing…
How far have you come on your home made optical spectrometer and how far have you gone with your book on ancient trade routes? I haven’t heard from you for a while and am still quite interested in how your projects are coming along. Please let me know by private message if you are so inclined. Thanks.