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Montroydite from Terlingua, Texas
  
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Tom Tucker




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PostPosted: Feb 02, 2017 17:45    Post subject: Montroydite from Terlingua, Texas  

Jordi queried if my red cinnabar crystals might have been montroydite. I'm sure they're not, but we did see some apparent montroydite on one collecting trip.
An old college friend had been visiting the Terlingua area the previous week and had met a fellow who showed her a flat of apparent montroydite which included spectacular, large specimens for the species and locality. I believe they were not from the well known Mariposa Mine, but were from a "tourist" mine where the fellow worked as a guide for tourists, and was able to dig for specimens.
The following week my wife and I joined our friend, (all having been in the same college group in Missouri, and now working in scenic Midland, Texas), and visited a number of mines and outcrops around Terlingua. Later in the day Anita suggested we visit the fellow with the montroydite, which we did. He seemed to have his eye on Anita, a recent college graduate. He was one armed, and had recently been released from a prison. We asked about the specimens he had shown her the week before, and he brought out the flat - essentially empty. But, there were a number of fragments - brilliant, lustrous cherry red centimeter long prismatic slivers of montroydite, apparently with traces of native mercury along some of the edges. Just these dregs were spectacular - nicer than any of the photographed specimens I've found on The Web.
Apparently someone, reportedly from a museum in Houston, had come along during the previous week, and had purchased the entire flat. At least that's what we were told. This was in 1971. I have inquired of folks from the Houston Museum if they were the purchasers, and none knew of the material. I think I asked Art Smith, well known Houston collector, to inquire in the area, but I was never able to learn where the material had gone.
In the end, our one-armed friend gave a small crystal to Anita, but I was too dumb to also grab one.
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Jordi Fabre
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PostPosted: Feb 16, 2017 17:23    Post subject: Re: Montroydite from Terlingua, Texas  

Good history Tom.

The funniest thing is that maybe whoever bought that flat was Bill Pinch and that what you lost in fact was probably not Montroydite but Comancheite! ;-) :
Stories and historical value
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cascaillou




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PostPosted: Feb 22, 2017 13:08    Post subject: Re: Montroydite from Terlingua, Texas  

haha! I'm struggling to get my hands on a good specimen of montroydite (which is highly toxic btw). I actually missed a really good one a few years ago:

http://www.mineralman.com/ebay2/montroydite1009140009.jpg
(Link normalized by FMF)
Specimen size: 5.76cm x 4.65cm x 2.72cm
Locality: Terlingua, USA

That is a large aggregate for this rare species, and the specimen had some aesthetics thanks to the calcite.

I wonder if a trip to Spain (which has several mercury mines) would be worth a try, any montroydite reported there Jordi?
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lluis




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PostPosted: Feb 22, 2017 14:47    Post subject: Re: Montroydite from Terlingua, Texas  

Good afternoon, Cascaillou

Well, in Spain, *several* would mean few ones...
The main was Almadén (gone.....), and one in Leon... Not too much in my humble point of view....
For Montroydite... I have never seen a spanish exemplar... And I collect systematic...
So, if you wish to come, you are welcome (and invited to home, by the way)...But chances are so low..... :-(

With best wishes

Lluís
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cascaillou




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PostPosted: Feb 22, 2017 19:03    Post subject: Re: Montroydite from Terlingua, Texas  

Good evening Lluis :-)

Mindat list 7 spanish mines, with reports of both cinnabar and native mercury (calomel was also reported in 4 of these).
However 5 actually belong to Almaden district, and only 2 mines don't.
https://www.mindat.org/minlocsearch.php?frm_id=mls&cform_is_valid=1&cf_mls_page=1&minname=mercury&region=spain

However there isn't any report of montroydite from spain on mindat. I wonder which of these mines (if any) could be worth considering for this specie...

But you're probably right, what are the odds? Anyway, thanks for your welcoming :-)

Also, another concern is about accessibility of those mines. Are the tunnels/shafts still open? Are some of these mines open-pit (i.e. surface) works?
Indeed my concern is that exploration of these mines might require going down deep shafts, which would require some serious experience of speleology.
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Matt_Zukowski
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PostPosted: Feb 22, 2017 20:05    Post subject: Re: Montroydite from Terlingua, Texas  

To evaluate the odds of finding montroydite in Spanish mines, I'd ask myself what is unique about Terlingua that allowed HgO to form and then try to determine if those same conditions exist(ed) in Spain.

I'd also ask myself if there are any other minerals at Terlingua that formed because of the conditions that allowed HgO to form. This might give you an idea of associated minerals that could indicate the presence of HgO. Then see if any of these associated minerals are found in Spain.
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cascaillou




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PostPosted: Feb 23, 2017 11:15    Post subject: Re: Montroydite from Terlingua, Texas  

Montroydite occurs in oxidized hydrothermal mercury deposits (it's a secondary mineral found in the oxidized zone of some mercury deposits), and associated minerals include mercury, cinnabar, metacinnabar, calomel, eglestonite, terlinguaite, mosesite, kleinite, edgarbaileyite, gypsum, calcite, dolomite.

Mercury, cinnabar, calomel, eglestonite, calcite and dolomite have all been reported from La Cena del Depósito concession (located in Almeria province).
But I also found a report of microscopic montroydite from Almaden mines (located in Ciudad Real province), however I can't say how the specimen was analyzed. Almaden mines have mercury, cinnabar, metacinnabar, calomel, gypsum, calcite, dolomite.
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lluis




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PostPosted: Feb 23, 2017 11:28    Post subject: Re: Montroydite from Terlingua, Texas  

Thanks for comments, Cascaillou

For montroydite, mercury oxide, I would fear that it could occur where there is not sulphide.
Mercury has a too big affinity with sulphur, and if it is there, few montroydite you could expect to find....(if any....)

If analysis are well done.... I have a piece of almandine that previously has been labeled as zircon and later as corundum....... (and not by first timers collectors, but for well knowledgeable ones. True come with Fabre analysis...). So.... As all, depending in quality..

With best wishes

Lluís
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cascaillou




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PostPosted: Feb 23, 2017 12:28    Post subject: Re: Montroydite from Terlingua, Texas  

I don't know, montroydite occurs in cinnabar desposits, and cinnabar is a sulfide afterall. Apparently, montroydite tends to occur where there is calcite (and dolomite), and one should look in the oxidized zone of the deposit.

PS: red garnet vs red zircon vs red corundum: a handheld diffraction grating spectroscope could have been helpful (provided some transluscency was present, at least on the edges).
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lluis




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PostPosted: Feb 23, 2017 13:51    Post subject: Re: Montroydite from Terlingua, Texas  

Cascaillou

If there is sulphides, montroydite would convert to any mercury sulphide,,,, Just chemistry.
That maybe it is oxidized, and with contact with carbonate it leads to mercury oxide, it is a possibility, of course... I just do not know.... But in Almadén, where mines where, as far as I know underground, far under, well, oxidation zones seems not to probable to my understanding.... But....
Just chemist.... :-(

For what you say about the pyrope (sorry, previously I said almandine, but is a pyrope from USA, no more details), agreed.
Just that was not done by the previous owners....
I have also a piece of a complex sulphide, with analysis provided (XRF), with data.
Attribution was bad done, just regarding analysis. Done by a so called premium dealer in USA. Doing maths, it is another thing. And was confirmed by Joan Viñals....
So, as I said, well done analysis, well, exist. As well as bad done ones.... :-(

With best wishes

Lluís
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cascaillou




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PostPosted: Feb 23, 2017 16:33    Post subject: Re: Montroydite from Terlingua, Texas  

Actually, there's an open air mine in Almaden district (El Entredicho Mine).

Anyway, it isn't a matter of underground or open-air mining. Indeed, the oxidized zone of a deposit results from surface water permeating the underlying rocks (I mean well before humans even considered digging into the ground), which is called supergene process.

As a side note, in the lab, mercuric oxide can be prepared either by heating Hg in oxygen at roughly 350 °C, or through precipitation of aqueous Hg2+ with alkali.
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