FMF - Friends of Minerals Forum, discussion and message board

[Turbo]

Does anyone know anything about yellow apatite from "Lake Jaco?" There is a cut stone that I'm interested in to go with a rough from Cerro de Mercado, but it's locality in Mexico is not confirmed. The gem is 23 cts., so it is a pretty large size. The question is whether it is likely to be from purported finds in Lake Jaco or from the more well known Cerro de Mercado site. Information affects value, so I'd like to know as much as I can.

Ed Bayley

[Peter Megaw]

I have never heard of apatite from the Sierra Las Cruces (aka Lake Jaco) locality. This is a skarn system with abundant garnets (black, pink, white, yellow, green, red) and vesuvianite with rare scapolite and rarer base metal oxides (it appears to be a HUGE barren skarn). Some of the vesuvianites get close to gemmy so it is possible that someone cut one of them and got a stone that resembles apatite, but I am not aware of any apatite found there...but certainly not in quality to be mistaken for Cerro de Mercado...and even less likely to be 23 carats.

If it's classic Cerro de Mercado "asparagusstone" color, it's 99.99% sure its from there

Virgil Lueth at New Mexico Tech probably knows the locality better than almost anyone else...although Dennis Beals (XTAL) is catching up quickly.

[Turbo]

I would say it does have that classic Cerro de Mercado "asparagusstone" color. The dealer had said that the "Lake Jaco area" was producing apatite again (I guess in the past couple of years) and that it had in the past as well. You probably have more knowledge, so he is probably mistaken. I don't know Virgil Lueth personally. Do you think he would mind if I sent him an e-mail?

[Peter Megaw]

I'm sure Virgil would welcome an e-mail. I am not sure how a locality can produce again if it hasn't before...I think your dealer is confused. If not, I want/need one of these for my collection.

[GneissWare]

I collected for several years at the "Lake Jaco" (Sierra Las Cruces) locality, and there is no apatite present.
Bob

[Turbo]

I thank you for all the insight. I was hoping it was a Cerro de Mercado. Have there been recent finds of high-carat gem grade material from Cerro de Mercado?

[Pete Modreski]

A fellow from Mexico was selling Cerro Mercado apatite at the "Contin-Tail" rock swap in Colorado this summmer. He had a table full of material, from loose crystals to matrix specimens, a few large "museum size". It gave me the impression that a fair quantity of apatite must be being mined there right now. Here, I'll attach one of the pictures I took of them there.

[Peter Megaw]

Cerro de Mercado was closed during most of the 90s and into the early 2000s. With the spike in iron prices over the last decade it was put back into full production after a modernization of the plant and installation of magnetic separators. These separators allowed them to crush lower grade ores finely and separate the iron minerals from the "trash"...volcanic host rocks, chalcedony and apatite, and make a high-purity, low apatite iron concentrate. Removal of apatite is especially important because phosphorous causes real problems in the smelting/foundry process. Previously, CdM operated with sorting belts where workers hand picked the crystals of apatite and lumps of apatite bearing breccia as they came by. The apaptite crystals went into buckets and you could buy them at the mine office for a pittance. Today many fewer apatites are emerging because the only ones being produced are those the equipment operators find in the pit. The good side of this is that they ones they find tend to be large and flashy...and they collect them before they get too heavily blasted. Since the apatites tend to occur in late vertically persistent breccia bodies that cut the massive iron ores, they learn where the best bodies are and keep an eye on them for specimens.

The picture Pete provided looks like classic breccia material...matrix of magnetite-hematite supporting large apatites that are in turn cemented with late chalcdeony. I have seen a fair amount of this material recently and am not surprised that 20+ carat stones are being cut.

It has been a few years since I was in CdM, but I know it is producing at capacity and the orebody is being depleted. I suspect that we are probably nearing the end of its life and that these apatites will vanish from the market sooner rather than later...good time to get one (or more) of these classics

[Turbo]

Very cool. I'm glad I decided to add this apatite to my collection. Here is what Virgil Lueth said:

"I agree with you and Peter that the stone is probably from Cerro de Mercado. Although the geology is correct for the possibility of gem apatite at Hercules (Sierra de Cruces iron deposits), I've never seen any gem apatites from the Lake Jaco (Sierra de Cruces) area."

[Peter Megaw]

Interesting Virgil should mention Hercules. This is a highly productive iron mine in the middle of nowhere...never heard of apatite from there, but it does have martite that looks very much like Cerro de Mercado...except it has good lustre.

What Hercules has, although lamentably little gets out because of its remoteness, is calcites reminiscent of the best from the Cumberland, England iron fields. These range from gemmy water clear (almost impossible to photogragh well) to red-pink crystals filled with hematite dust inclusions. Fishtail or "Bishop's Mitre" twins are common, though small.

Some shots below

[Turbo]

Those calcites are gorgeous. I am beginning to find Mexican mineralogy very interesting.

[Peter Megaw]

In case you needed a push getting over the edge regarding Mexico...here are some more shots of what Mexico can do...subtle it ain't

[Turbo]

Very tantalizing! I see Mexico as a likely focus for my collection as it develops.

[javmex2]

Hello. very interesting topic on the minerals in Mexico, thanks to Peter, I'd love to see the best of his collection,

[Peter Megaw]

When you visit Tucson...tienes tu casa!