Vesuvianite from Georgetown / California ?

I recently bought a specimen of vesuvianite, which I clean at the moment, pics will follow the next days.
The label tells "Georgetown, California / USA", the specimen identification says Vesuvianite (Idocrase).
This brought me to location # 69060, Stifle Memorial claim, Georgetown Dist.
There are no images available from specimen of this loc.

Does anyone have pics of specimen from there, or do you have specimen in your collections and could add images?

Thanks,

Christian

I have not found a picture but I did manage to find a discription of the crystals found there:

"Small emerald green prismatic crystals of gem quality have been found at Georgetown, California."

You may also like to read this about vesuvianite from georgetown, CA:
(http://www.minsocam.org/ammin/AM21/AM21_1.pdf)

Some additional information about the find:

"Abstract Chemical analysis (including H2, F2, FeO, Fe2O3) of a Mg-vesuvianite from Georgetown, Calif., USA, yields a formula, Ca18.92Mg1.88Fe3+0.40Al10.97Si17.81- O69.0.1(OH)8.84F0.14, in good agreement on a cation basis with the analysis reported by Pabst (1936). X-ray and electron diffraction reveal sharp reflections violating the space group P4/nnc as consistent with domains having space groups P4/n and P4nc. Refinement of the average crystal structure in space group P4/nnc is consistent with occupancy of the A site with Al, of the half-occupied B site by 0.8 Mg and 0.2 Fe, of the half-occupied C site by Ca, of the Ca (1,2,3) sites by Ca, and the OH and O(10) sites by OH and O. We infer an idealized formula for Mg-vesuvianite to be Ca19Mg(MgAl7)Al4Si18O69(OH)9, which is related to Fe3+-vesuvianite by the substitutions Mg + OH = Fe3+ + O in the B and O(10) sites and Fe3+ = Al in the AlFe site.

Thermodynamic calculations using this formula for Mg-vesuvianite are consistent with the phase equilibria of Hochella, Liou, Keskinen & Kim (1982) but inconsistent with those of Olesch (1978). Further work is needed in determining the composition and entropy of synthetic vs natural vesuvianite before quantitative phase equilibria can be dependably generated. A qualitative analysis of reactions in the system CaO-MgO-Al2O3-SiO2-H2O-CO2 shows that assemblages with Mg-vesuvianite are stable to high T in the absence of quartz and require water-rich conditions (XH2O > 0.8). In the presence of wollastonite, Mg-vesuvianite requires very water-rich conditions (XH2O > 0.97)."

Hi Mike,

thanks for this information! I already had "Small emerald green prismatic crystals of gem quality have been found at Georgetown, California.", found it via Google, and this is what makes me doubt the loc for my specimen.
The crystals are about 3 cm across and are shaped like the ones from China, but green.
I will have to do pics and place them here.

Christian

allright, the data and the pics:
specimen size 13.2 x 9.4 x 6.5 cm.
biggest vesuvianite is 5.2 cm across, colour in person is more brownish-green than the brown the pics show.
some crystals show thin layer of brown garnet.
locality named is Georgetown, California / USA, specimen was purchased in 1980 by a german collector.

2nd pic



Edited 1 time(s). Last edit at 04/18/2008 03:22PM by Christian Bracke.

crystal of 5.2 cm across !

4th pic

5th pic

last pic...

take your time, I´ll be back on monday morning, and I´m curious what you guys can tell me...

Have a great weekend,

Christian

I would pretty much appreciate to get californian and US-collectors comments on this specimen.

thanks,

Christian

Hi, Christian.
I live and collect in Northern California. What I've heard of California Vesuvianite, is that the bigger specimens usually do have a thin garnet crust.
While I do not have this in my collection, I happen to be going through Georgetown on my collecting trip next week. I will check out the locations in the paper Mike posted, and also check shops in the area. If I can find (or find out) anything, I'll post upon my return, after the first weekend in May.

Corie
Ps, it is a stunning piece, absolutely beautiful!

Hi Christian,

Your specimen is very typical of the material found at the Feather River locality near Portola, Plumas Co. California. I have collected there and strongly believe that your specimen is from this location. I don't know of any other northern California locations that produce specimens like this. The predominate associated mineral at this locale is blue calcite, which most specimens are etched out of. Any signs of the calcite remaining on the specimen would further substantiate this as the locality.

Yours would be a very nice specimen from this location.

Eugene

@Corie
Hi Corie,
some vesuvianite crystals indeed show a thin, brownish crust which I identified as garnet. I appreciate your support and hardly can wait for your information after you returned from that trip in early May. Is there a museum which may have specimen like this?
P.S.: I like this specimen as well, no matter where it comes from, it´s not too bad for the mineral... ;-)))

@Eugene
Hi Eugene,
thanks for your support! How far is the Feather River loc. away from the Georgetown locality? The condition of some vesuvianites on my specimen would fit into your idea that they were etched out of calcite, even if there are no calcites remaining. Do you have images available from specimen of Feather River?

Thanks guys! Looking for more info from you. ;-)))

Anybody else with information ???

Christian

@Eugene
what I found out is that the straight distance between Georgetown and Feather River is about 70 miles or so, could it be the same geological structure, anyway?

Christian

Nobody else familiar with this locality, or at least can identify the correct locality for this specimen?

Christian

Christian,
The area is where the edge of the north american plate pushed over the farallon plate, creating the Sierras. Both areas are directly at the foot and same elevation, so one could assume the same geological structure.

I'll find out next week, though!
This is exactly what I love about minerals. There's a question, you go out, hands on, and get an answer. YAY!

Corie

Corie,

so this specimen could be from one or the other locality, according to the geological structure, fine.

I really appreciate your support, and I think in the same way as you do.
I am specialized in swiss alpine minerals, and whenever there´s a question regarding this area I check out during my next stay and most times get a satisfying result. I love it!

What is strange regarding this specimen is, that not more people can tell something about it. When I got the specimen about ten days ago my expectation was that I got an average specimen from a well known locality, and I expected to find information and photos of similar specimen, here in mindat and in the web. Surprisingly I only got a few (important) information, but not too many people seem to know about this loc. and similar vesuvianites.
I wonder if there a specimen in collections of local collectors, museums or dealers...

Thanks for now Corie,

Christian

Christian,

This is a well known locality, but very hard to get good specimens from. The outcrop is huge, perhaps 50' x 25' exposed. Most of it is massive with veins of bluish calcite. This is where the Vesuvianite is crystalized and well formed. Your specimen is one of the best that I have seen from the location. There are examples on various web sites and if you Google Vesuvianite and Plumas, you can find some photos, though not as fine as your specimen.

Ciao,
Eugene

Eugene,

I did google for Vesuvianite and Plumas and were successful, especially the specimen of the NHM of LA County (adopt-a-mineral page) shows a very similar specimen with two intergrown, lustrous crystals of about the same size as mine are.
So I now can be sure it´s a californian vesuvianite.
When Corie returns from his trip and tells his news I will be able to post my pics, I think.

Thanks Eugene,

Christian

Someone else with info?

Christian

@ Corie

Any news from last weeks trip?

Christian

Christian,
It is good to be home!
I have news - your vesuvianite is most likely not from Georgetown.

I spoke with a woman who knew Mr. Stifle, the man who mined vesuvianite from Georgetown after he retired from the Army after WW1.
He found several veins of vesuvianite coming through the serpentine on his property, but the crystals were all very small, none larger than a half inch (and those were rare) and brilliant green.
I have heard that clusters were found, but again, tiny crystals, brilliant green.
He sold the individual stones in town for 25 cents each, labeled as "Georgetown Emeralds"!

The woman I spoke to believed your specimen may come from Riverside or Calaveras Counties, if it came from California. She had heard of large sized crystals in clusters from there, and was not surprised by the garnet encrustation.

I hope this information helps, but I think it may create more questions!

Best Regards,
Corie

Hi Corie,

thank you very very much for your research work!
The information fits into the comment of Eugene, who mentioned that this specimen wouldn´t be from Georgetown, but from the Feather River locality near Portola, Plumas Co. California.
This is little north of Calaveras Co., so may fit together well.

For me your information does not create new questions, because together with my additional web-surch and a check of a specimen in a german museum I am sure it is from Plumas Co.

I want to thank all involved people for your support, good job !!!

Christian

Excellent, Christian!
I'm glad you got that question answered, and am happy I could help!
I love the research process.

Corie

Hi Corie,

I do prefer to have proper information on the label with the specimen, but if questions turn out to be answered like this, I love it as well!

Have a great weekend,

Christian