FMF - Friends of Minerals Forum, discussion and message board

[Tobi]

Hi all,

some time ago a fellow collector told me that the famous pink grossulars from Sierra de Cruces in Mexico ( https://www.mindat.org/loc-5433.html ) are treated to get this great colour and that they were actually pale, with a colour like human skin. After a discussion on German Mineralienatlas board most others said they never heard of that and that the exceptional colour of these garnets is completely natural, caused by manganese. Does anyone here have more information about this?

Thanks in advance!
Tobi

[keldjarn]

Tobi,

the "rasberry" colored grossular garnets I have from Mexico show colour zonation as would be expected from different composition of the fluids during growth. Also garnets totally enclosed in calcite have the same strong rasberry colour. I think these observations exclude the possibilities of any artificial origin of the colour. Variable Mn-contents in the different layers is a plausible explanation.

Knut

[Jordi Fabre]

I totally agree with Knut. In fact I never heard nothing about anthropogenic improvement of the color of these garnets, so it could be a very local history due to the intense color of the garnets, or maybe some of these garnet were covered by Paraloid or similar (please see: Repairing mineral specimens) to avoid them to fall down of its matrix and that cover improves a little bit its color...

[Riccardo Modanesi]

Hi to everybody!
An interesting article on the magazine "GEMMOLOGIE" from the German Gemological Association in Idar-Oberstein came out recently about these pink and green grossulars from Mexico. Some of them have a pink coloured covering and a green core inside. I have also a raw specimen of pink grossularia from Mexico, typical rhombododecahedral crystals on rock, the biggest one is some 4 mm diameter.
Greetings from Italy by Riccardo.

[Tobi]

Thanks! I'm expecting such a specimen and if i keep it as new addition to my collection, i would not want to have something manipulated. I knew about the zoning: All of those garnets seem to have a dark core under the pink surface. I only wanted to ask if something was done to make that colour better. It is good to be careful when something seems "too" nice. And garnets with a colour like Sweet Home Mine rhodos are not really something you expect. So much the better if it was nature and not men who made those wonderful crystals :)

[GneissWare]

The old big pink garnets, once called Roselite, were collected in the late 1950s to early 1960s by George Burnham of Burminco (Monrovia, CA). Based on his contemporaneous field notes, they were pink when found. As for the other garnets (red and raspberry), I have collected both in situ and they are that color in the ground.

I have not tested the big pink ones for luster enhancement, and have been suspicious of that aspect only.
-Bob

[lluis]

Dear All

Well, I have never read nothing about color enhancing of garnets (and God knows that I am interested in colour enhancement treatments because I have worked when a little kid for a gems' dealer and I like a lot cut stones; yes, my sin.... :-( ; to hear that many yellow corundum are treated, well, makes me not very happy.....)

Other, as Jordi and GneissWare pointed, is if someone covered them with colour enhanced Paraloid or the equivalent, to enhance luster and color.

But if we come to that, maybe we should place a look in some chinese rhodos with astronomical prices..... :-(

Anyway, some time ago (7-10 years....; infinite patience....) I have heard direct from a rock hound about amethyst colored Jeffrey Mine garnets. Not the pink ones, but lilac.
Some found, sold, never more heard, never more seen....

With best wishes

Lluís (any lilac Jeffrey garnet for a collector.... :-) ? It would have a good home! )

[Elise]

Hi,

Just to add a bit more -- on another thread about these garnets, I posted a portrait Jeff Scovil took in 2011 of my small collection of them https://www.mineral-forum.com/message-board/viewtopic.php?p=15771&highlight=#15771 It shows the deep color and the core (I had started the thread to inquire about the color and fluorescence).

Cheers!
Elise

[Jean Sendero]

Interesting, concept but so unlikely.

Dennis Beals that mined the area a few years back showed me photographs of the garnets, pink or red depending on where they were from in the "vein" that were in-situ, still in place in the bedrock.

Also Virgil Lueth presented a paper at the New Mexico Mineral Symposium of 2002. You can find the abstract following this link on page 133. ( https://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/24/n4/minsymp.pdf / link normalized by FMF). The title of the paper was "Red Garnets from Lake Jaco, Mexico, and the chemical controls of color in Garnets".

Happy reading and I hope that the skeptics will now be believers.

Cheers

Jean

[GneissWare]

These are definitely from the later find -- Graham Sutton and I found the deposit in 1993; Dennis is currently mining them. They are natural and unenhanced.

[Peter Megaw]

The color of these garnets, and similar manganese-rich garrnets from Morelos State, Mexico is natural. It is quite likely that some specimens have benefited from "luster in a can", especially the mass processed commercial level material.

It bears repeating that George Burnham (Burminco), in adddition to bringing out a lot of good specimens, is responsible for the mis-naming or misattribution of these garnets as "Lake Jaco" Chihuahua...it was his dodge to eliminate competition. The garnets come from the Sierra Las Cruces, which is in Coahuila State, east of Lake Jaco in the Sierra Mojada Muncipality. Lake Jaco should be eliminated from your labels.

There is an excellent article on the locality by Virgil Lueth in Mineralogical Record's third Mexico issue...volume 34 #6.

[Dennis Beals]

Hi Tobi,
I have been mining this location for the last few years. The color is quite natural. It varies quite a bit and the very best color came from the Cerro de Moki which is only a short distance from where I dig. That location was mined out. If you are interested in seeing more about it, my facebook page has an album about the location including in situ fotos and no I don't own a copy of photoshop!
Dennis

[Tobi]

Thank you all!

And Dennis, i browsed your Mining in Mexico album: Very nice photos, the garnets you found are really fine. And natural ;)