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28 Mar-18:25:15 Re: collection of firmo espinar (Firmo Espinar)
28 Mar-09:37:50 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Cfrench58)
27 Mar-19:47:08 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Pete Richards)
27 Mar-16:15:44 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Cfrench58)
27 Mar-15:18:59 Re: 2 unknowns co-occurring with caledonite, grand reef mine, az (Alfredo)
27 Mar-14:39:29 2 unknowns co-occurring with caledonite, grand reef mine, az (Cfrench58)
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27 Mar-02:39:50 Re: the mim museum in beirut, lebanon (Tobi)
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26 Mar-00:53:41 Re: collection of volkmar stingl (Volkmar Stingl)
25 Mar-13:32:10 Re: collection of michael shaw (Michael Shaw)
25 Mar-00:25:58 The mizunaka collection - quartz (Am Mizunaka)
23 Mar-13:35:22 Re: collection of firmo espinar (Firmo Espinar)
22 Mar-08:32:28 Re: collection of michael shaw (Michael Shaw)
22 Mar-04:20:41 Re: the mim museum in beirut, lebanon (Mim Museum)
21 Mar-22:49:19 Re: green seam. Looks like it in a state of decay. (Ning)
21 Mar-22:47:40 Re: green seam. Looks like it in a state of decay. (Ning)
21 Mar-22:45:25 Re: green seam. Looks like it in a state of decay. (Ning)
21 Mar-15:34:23 Re: the mizunaka collection - quartz (Am Mizunaka)
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21 Mar-14:15:36 The 4th phoenix heritage mineral show (phms) hosted by mineralogical society of arizona (m (Chris Whitney-smith)
21 Mar-04:36:10 Re: the mizunaka collection (Tobi)
21 Mar-04:11:47 Re: jim’s mineral collection (James Catmur)
20 Mar-23:34:15 The mizunaka collection - quartz (Am Mizunaka)

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EDS Testing of Gold Jewelry
  
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Lucca




Joined: 06 Oct 2017
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PostPosted: Oct 07, 2017 16:28    Post subject: EDS Testing of Gold Jewelry  

A colleague and I engaged in EDS (energy-dispersive X-ray spectrometery) testing gold ore in jewelry. In one test we found in order of abundance: Ag, Te. then S. To our best knowledge the provenance of the ore is that it derives from either California or Arizona. There was no Cu.

My question is: What mineral is it likely to be? the gold was found in a dark to black matrix.

I thank you for any assistance. Mineralogy is not my field.

Henry
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Bob Carnein




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PostPosted: Oct 07, 2017 17:44    Post subject: Re: EDS Testing of Gold Jewelry  

Hessite is silver telluride (with a 1:1 Ag:S atomic ratio). The sulfur may be present in another mineral; because of its large ionic radius, the Te ion doesn't substitute for sulfur, making it unlikely that the mineral is a silver sulfide (e.g. acanthite) with Te replacing S. It's also possible that the sample contains acanthite with native tellurium.
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Peter Lemkin




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PostPosted: Oct 07, 2017 23:16    Post subject: Re: EDS Testing of Gold Jewelry  

Calaverite is a rather rare gold telluride with the formula AuTe2. But there are five others. In the USA, as far as I know two of these were 'common' only in Cripple Creek, Colorado. Also found in Kalgoorlie, Australia and Ontario. There is a good technical article on processing of such ores:
https://www.911metallurgist.com/blog/wp-content/uploads/2016/09/Recovering-Gold-from-Telluride-Ore.pdf
(link normalized by FMF)

I would think this gold was from a gold telluride or some telluride was used to process the ore. At about half the price of Gold, Tellurium is too expensive to toss into the 'pot' without a reason.
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Peter Lemkin




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PostPosted: Oct 08, 2017 04:43    Post subject: Re: EDS Testing of Gold Jewelry  

An aside: While I have no gold tellurides in my collection ;-(, I once had the privilege to examine in my hands some fantastic specimens of calavarite xx from Telluride, CO! Sadly, they are not on display anywhere - but stored away for some future ? museum display in San Miguel Co., CO. These were really spectacular crystals!, although large quantities were not found in Telluride well crystallized and large - or perhaps were, and (as so often during the 1800 mining era) tossed into the ore cars along with the common 'ugly' ores.
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