FMF - Friends of Minerals Forum, discussion and message board

[Tracy]

At last, now that I have good photos to share...

In a posting last September I asked if anyone would be willing to help identify a "mystery" specimen that has been in my possession since 1994. John White was kind enough to look at it and had a fragment optically analyzed. The results indicated it was fluoroapophyllite, but John was unsure about the locality because of my specimen's unusual crystal habit.

Recently I sent the specimen to another mineral enthusiast, and I am happy to report that, after conferring with other collectors/experts, he informs me that the locality is San Martin, Mun. de Sombrerete, Zacatecas, Mexico. My "mystery specimen" now has an identity!

Allow me to give credit where credit is due: to John for confirming that it is fluoroapophyllite, to Russ Rizzo of Cal Neva Minerals for narrowing its origin down to Mexico (and for the photos too), and to Cal Graeber for pinpointing the locality as San Martin. I also wish to thank Jordi and his Forum for giving me the inspiration as well as the opportunity to have an "identification adventure." It's been a very rewarding and informative experience for me. :-)

[Tracy]

I forgot to provide dimensions: it is approximately 4 inches (10 cm) at its widest point - the specimen has no "top" or "bottom."

[Tracy]

I finally have a few minutes to give an update on mymystery specimen:

After seeing the pink fluorapophyllite specimen at the Smithsonian from Guanajuato which looked very much like my own piece (see the photo I posted in the "Visiting the Smithsonian" topic), John was kind enough to put me in contact with Peter Megaw, who shared the following interesting information about Mexican fluorapophyllites:

"[Zacatecas, Guanajuato, and Naica] have produced lovely DT transparent pink crystals that are difficult to tell apart without some matrix. Many of the San Martin specimens (probably truly removed from the adjoining Sabinas Mine...same orebody different owner) have crumbly laumontite associated and a few have nice sharp lustrous ilvaite as well. Since this is a skarn, sometimes they have garnet-pyroxene skarn on the matrix, but most tend to peel off leaving nothing behind the crystals. Naica, also a skarn, has the same matrix situation...but I don't know of any associated species. Naica crystals do tend to be a bit squatter and blockier. Guanajuato material tends to be plates of crystals with few associates...but clear quartz vein matrix."

I sent Peter the photos above of my specimen, plus two more from different sides (attached below), and got a quick response from him:

"Tracy, Nice piece! Looks like your "logs" are quartz crystals coated by the apophyllite. Given the age of the piece and the coated quartz crystals it is probably from Guanajuato. Naica and San Martin didn't produce pink apophyllite until the late 90s and I have never seen this kind of coating at either of those places.

Please let me know if you ever decide to trade or otherwise dispose of the piece!

Peter"

...I really enjoyed reading that last sentence! (but have no plans to trade) :-)

Note that the "logs" refer to the hexagional crystals which appear among the mineral shards. There are 3 of them, the largest of which is in the photos above and the two smaller ones in the photos below (the smaller ones have a limonite-like coating on them, the large "log" is only partially coated with the same on the "rear" side). As a reminder, I acquired the specimen c. 1994.

So, it seems I will have to change my labels from Zacatecas to Guanajuato. I wish I could pinpoint the actual mine, but there are many mines at Guanajuato and I am happy enough to know where in Mexico it came from. Just thought I'd share what I learned from Peter.

Thanks to Peter and to John for all your help with solving this mystery!

Tracy

[Peter Megaw]

I think that the mystery may still stand...but will bow to Cal if he handled a number of specimens from this find. (By the way Cal, given the quality and quantity of what you're getting out of the Rogerley at last, I'm surprised you have time for answering questions like this! Keep it up...the new material sounds/looks great!!! Congratulations! There will never be doubt as to the source of those great twins!)

I have not seen this material before and may just have missed it. However, the specimen has several elongate quartz crystals under the apophyllite coating... which is more suggestive to me of Guanajuato than San Martin for several reasons. Guanajuato is an epithermal vein system with abundant quartz with this general morphology (as much as can be seen from the picture.) In contrast, San Martin is a skarn system which has less abundant quartz, generally with a prominent bulge in the middle...like Amatitlan, Guerrero. Further, the tabular apophyllite coated "chips" are very reminiscent of the platy calcite typical of epithermal veins everywhere...and very well known from Guanajuato...especially as quartz replacements. Similar epithermal textures are known at San Martin, but only in the upper oxidized zones.

I was also contacted by the specimen's owner and understand that this piece was acquired in the early 90s...this timing is better for Guanajuato than San Martin and only gets stronger if the specimen sat for a number of years before purchase. I checked my San Martin apophyllites, acquired in the mid 90s to 2007 and they all have tiny laumontite crystals in the matrix and on top of the apophyllites.

Someone should poll Dennis Beals on this...he was pulling material from both localities in this time frame!

[Tracy]

I must apologize for not finishing my homework on this one, and in the process inadvertently offending Cal or Peter. I should have continued with my pursuit of this question until consensus was achieved. Unfortunately, I did not have any contact information for Cal to complete the circle of discussion. It was never my intention to pit one expert against another, just to find answers to my question.

Peter, if you could provide me with contact info for Cal (his response came to me second-hand), I would like to consult with him on this too and complete the loop (or Cal, if you have been reading this and wouldn't mind commenting on this thread, I'd be grateful).

Thanks (and sorry)
Tracy

[Tracy]

Just to make sure that everyone looks at all the same images, here is the Guanjauato specimen seen at the Smithsonian...

[GneissWare]

Hi Tracy,

Cal's e-mail (I think) is : cgraeber (at) tfb (dot) com
Dennis' is: dbxtal (at) aol (dot) com
His website is www (dot) xtal-dbeals (dot) com

I would probably give Dennis first try.

Bob

[Gail]

cal(at)calgraeber(dot)com is the address I have for him.

[Tracy]

Rather belatedly, and now that I'm on vacation (at last!) - thanks Bob & Gail, will pursue new leads and keep you posted.

Tracy

[Tracy]

My last posting out of Springfield - according to Dennis Beals, who took a look at the specimen last weekend, it is from Guanajuato. Dennis said that something as brecciated as my specimen would not have come from anywhere else in Mexico where pink fluorapophyllites are found. He also said that the piece might easily have been mistaken as being from San Martin because of the quartzes present in the mix, but that pretty much all the older specimens of this type emanated from Guanajuato. He also advised me to get it cleaned! - and thinks that the largest quartz "log" which you can see in the photos is a smoky. Another vote for Guanajuato...