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Red or pink Grossular Garnet, Mexico
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Elise




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PostPosted: Feb 25, 2010 14:49    Post subject: Red or pink Grossular Garnet, Mexico  

Hi,
I am trying to find out more about this type of pink grossular; specifically I am looking for the high end of RI range, UV reaction and the spectrum (or any references someone can point me to). From different references including MinRec and the Garnet Lithographie issue, the Jeffrey Mine Canada and the Lake Jaco Chihuahua or Coahuila states in Mexico seem to be the sources and somewhere else in my notes, I have also the state of Morelos.

In the references above, it indicates that it is one of the few garnets which fluoresce ("scarlet red" under SW, due to the Mn). I would think that any iron would quench that effect, but it is indicated that Fe concentration is very low. Are there transparent crystals which do not have the high Ti and Fe andradite cores and are not so included? And do the transparent crystals, including those from Morelos, always fluoresce?

Best wishes,
Elise

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Peter Megaw
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PostPosted: Feb 25, 2010 15:31    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Elise: Virgil Lueth at New Mexico Tech has done a fair amount of work on the garnets from northern Mexico...what you're calling Lake Jaco. The correct locality is Sierra de las Cruces in Coahuila...just east of Lake Jaco. It is a very extensive Mn-rich skarn system. I have seen a wide range of garnets from there, some with dark cores and some very pale grey or pink to the core. Virgil can probably help you out on those.

The Morelos locality you refer to is another skarn system near a village of Xalostoc...my Mexican company happens to own the locality. The garnets I have seen from there are pink to the core, but I have never lamped them.

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Antonio Alcaide
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PostPosted: Feb 25, 2010 16:04    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Hi, Elise, reading your comments I cannot avoid posting my favourite piece from Sierra de las Cruces, Coahuila. I am always looking for something like that, but I haven't had luck. I picked it from Jordi Fabre's web long time ago, before belonging this message board. I have no the exact reference. Please, pay attention to the white grossular garnets. The combo with the vesuvianite xls. is perfect.

Pink garnets from there are usually damaged, I love them though.

Greetings



Vesuvianite.jpg
 Description:
Vesuvianite and grossular garnets. Sierra de las Cruces. Coahuila. Mexico. Fabre minerals
 Viewed:  28026 Time(s)

Vesuvianite.jpg



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Ed Huskinson




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PostPosted: Feb 25, 2010 16:18    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Antonio Alcalde!!

Nice vesuvanite(s) specimen!!

I'm jealous. And you got it from Jordi too. So, double Woo Hoo for you.

Enjoy your specimen.

Ed

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Elise




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PostPosted: Feb 25, 2010 17:02    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Peter Megaw wrote:
The Morelos locality you refer to is another skarn system near a village of Xalostoc...my Mexican company happens to own the locality. The garnets I have seen from there are pink to the core, but I have never lamped them.

Peter, it was Virgil Leuth's MinRec Sierra de las Cruces paper which prompted me to post the topic because I was interested in the SW UV reaction.

From what I understand, the garnets from Morelos area are the ones which are reported to be more "gemmy" and are a draw for the facetors. I just wondered if they are similar to the Sierra de las Cruces locality as far as UV and RI. They seem to have made an appearance in the gem markets under various trade names. The mineral specimens are lovely as pictured in that article and in the Garnets issue.

Antonio - what a beautiful combination of minerals!

Elise

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Antonio Alcaide
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PostPosted: Feb 25, 2010 17:38    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Ed Huskinson wrote:
Antonio Alcalde!!

Nice vesuvanite(s) specimen!!

I'm jealous. And you got it from Jordi too. So, double Woo Hoo for you.

Enjoy your specimen.

Ed


Oh! No! I have made a mistake. I meant I picked the photo, not the specimen. Unfortunately. I do not think Jordi remember where the piece went. I would have paid a lot for it if I had been able. But I am a patient man. Maybe in the future.

I have a humble piece of vesuvianite, two. Without the garnets. Tomorrow I will post them. So don't worry, Ed. Both of us have similar luck.

Cheers,
Antonio

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Peter Megaw
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PostPosted: Feb 25, 2010 17:43    Post subject: Re: Red or pink Grossular Garnet, Mexico  

You're making me want to get out and dig some of the garnets in Morelos. At least locally they are abundant
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PostPosted: Feb 26, 2010 17:45    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Elise, I agree with you. Vesuvianite and white grossular garnets are amazing together.

Peter, do it for us. That thing: to look for garnets at Morelos makes me jealous. Maybe a day in the future I could go with you. Who knows?

best regards

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PostPosted: Feb 28, 2010 12:12    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Come on over...we're just getting this property going for gold exploration, which means we should be in and out over the next few years. I want to get a few big boulders of the garnet material carved out...the best zones I;ve seen run 35-50% garnet in white marble with some wollastonite.
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PostPosted: Feb 28, 2010 12:14    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Peter Megaw wrote:
Come on over...we're just getting this property going for gold exploration, which means we should be in and out over the next few years. I want to get a few big boulders of the garnet material carved out...the best zones I;ve seen run 35-50% garnet in white marble with some wollastonite.


Hi Peter,

Could you please find me a killer single in thumbnail size?!

Thanks,

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Peter Megaw
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PostPosted: Feb 28, 2010 12:17    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Most of the crystals are over an inch across
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Jordi Fabre
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PostPosted: Feb 28, 2010 13:08    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Jim wrote:
Hi Peter,
Could you please find me a killer single in thumbnail size?!
Thanks,

Please Jim, not bussines nor deals through FMF. Thanks!

Jordi
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PostPosted: Feb 28, 2010 13:18    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Jordi Fabre wrote:
Jim wrote:
Hi Peter,
Could you please find me a killer single in thumbnail size?!
Thanks,

Please Jim, not bussines nor deals through FMF. Thanks!

Jordi


Hi Jordi,

I thought I made an obvious joke! I'm well aware of the rules of the road, so to speak.

Cheers,

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Jason




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PostPosted: Apr 05, 2010 23:00    Post subject: Re: Red or pink Grossular Garnet, Mexico  

It's very rare to haver any garnets flour...since like you eluded to Iron tends to hamper that..what is unique is these mexican garnets you speak of..I have not had the pleasure of owning or having any..the grossulrs from Easdt Africa can and have been known to flour...they have a typical 400nm. which is cause for flour. in them..the gossulars from east africa tend and have the highest concentrations of calcium and a lack of anadradite there is in that locale..why..well east africa was a shallow sea for however many millions of years..seashells and calcium rich lifeforms flourished and died there..when you have lots of calcium rich things they tend to dilute iron which is universal in the earth crust..hecnee fine quality grossulars and flour. in them..maybe the same can be said about these mexican garnets...similar formation and environment..have you done a transmission spectrum on any yet, Elise?
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PostPosted: Jan 03, 2011 13:49    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Here is an example of one of the rarer colors of garnet from the Sierra de la Cruz, Mun. de Sierra Mojada, Coahuila, Mexico (Lake Jaco) locality. Graham Sutton and I found this piece and prepped it. It was later sold to the Pohl collection at the Freiburg Museum. The photo is a scan from a photographic print, so the quality is not so good.

By the way, a few years ago, George Rossman analyzed this color of garnet. I reproduce a portion of his note to me for those interested in the chemistry of these garnets.

"Results: The garnet is unambiguously a grossular

The approximate formula is (Ca 2.93 Mg 0.06) [Al 1.75 Fe 0.25] (SiO4)3

The chemical analysis indicates a little over 1% of the atoms are iron, but give no clue to its oxidation state.

However, the optical spectrum shows no trace of an almandine component which is easy to see in these spectra, so we conclude that the iron is present as Fe3+ which is much more difficult to see in the optical spectrum. Fully reasonable for a deposit that has manganese so oxidized.

So, we conclude that the garnet has a minor andradite component. This means that the iron replaces aluminum and would modify the color.

The magnesium would replace calcium for a minor pyrope component but not cause color.

What the quick analysis I ran did not show was any manganese. The conditions of the analysis would have shown Mn if it were present at more than about 0.1 wt%. A more careful (read more expensive) analysis would have picked it up, I am sure. The optical spectrum gives clear evidence for a trace of manganese in the garnet, and shows that much of it must be oxidized to the Mn3+ state (the dominant cause of the color of the garnet). This locality is known in the literature to produce the pink (raspberry) garnets that owe their color to Mn3+.

So, all said, we should call the garnet a grossular
It has a minor andradite component
It has a minor pyrope component

If you want to call components, this analysis of this particular spot would say:

Grossular 90
Andradite 8
pyrope 2"



garn001a.jpg
 Description:
Specimen approximately 16 cm across
Largest garnet is 7 cm across
 Viewed:  26550 Time(s)

garn001a.jpg


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Dennis Beals




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PostPosted: Jan 06, 2011 13:02    Post subject: Re: Red or pink Grossular Garnet, Mexico  

The very intense red grossular in very white matrix are from the Cerro de Moka, Sierra de Cruces, Mun. de Sierra Mojada, near Hercules, Coahuila, Mexico

This is a bluff a few kilometers to the southwest of the Santo Domingo Claim, Sierra de Cruces, Mun. de Sierra Mojada, near Hercules Coahuila. This is the locality with the black cores in a scapolite / wollastonite matrix and was first developed by Benny Fenn from 1995 - 2000.

The classic green and light pink garnets that were labeled Lake Jaco are found several kilometers to the northeast in decomposed matrix on the Alicante Ejido ranch, Sierra de Cruces, Mun. de Sierra Mojada,near Alicante, Coahuila, Mexico

This series of skarn deposits are hosted in a curving arc of hanging roof pendants on the southeast flank of the Sierra de Cruces.

Recent work on the Santo Domingo claim involved cleaning out the original hole, removal of overburden and then reversal of direction. The latest work has followed into an area with more massive vesuvianite matrix and less quartz. This allowed for larger crystals and more intense color. Less calcite in this area makes preparation much more difficult.

Good crystals of vesuvianite are relatively scarce as they tend to be very fragile.
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Jordi Fabre
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PostPosted: Jan 06, 2011 13:47    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Hi Dennis, welcome here!

Dennis carries with him PLENTY of amazing histories related with the mineral collecting in Mexico. We will be very lucky if he can find time and share them with us...

Welcome again Dennis.

Jordi
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PostPosted: Jan 06, 2011 13:48    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Hey, Dennis,
Nice to see you here!!!

You give a specific locality for the big pink, George Burnham era garnets. Have you actually visited it? We (Casey Jones, Graham Sutton and me) could never find it, even with Burnham's notes.

See you in Tucson, and bring me some unprepped stuff...maybe I'll bring you a gift too.
Bob
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PostPosted: Jan 06, 2011 14:13    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Hello to Everyone here

I have been a lurker here for a long time and as I have been doing more writing lately decided to join in the conversation.

I have not looked for the big pink locality as it is on a different ranch. The series of garnet localities stretch over a large area. The big pinks do not come from the Sierra de Cruces ranch and that only leaves the Alicante Ejido ranch.

This is a very rough area full of mesquite, cactus, ocotillo, scorpions and rattlesnakes. Finding an old picked over outcrop is problematic. One of the local vaqueros (cowboys) is looking into it for me.

Dennis
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PostPosted: Jan 06, 2011 14:37    Post subject: Re: Red or pink Grossular Garnet, Mexico  

Is that Miguel? Or Luis?
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