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Cahuille Mountains: pegmatite pocket?

Posted by Patrick Staeheli  
Cahuille Mountains: pegmatite pocket?
October 11, 2011 10:23PM
Hi
I am a new member of mindat.org and was just out in the Cahuilla Mountains to dig for tourmalines at a pegmatite. The schorl crystals are in a fine grained quartz matrix and can become quite large (up to 10”). However, there are no pockets and it needs some luck to get them out without too much damage. Most of them disintegrate while trying it. I found my best schorl after a lot of work on last Sunday and it measures just about 2.7” (attachment: tourmaline). So far, I didn’t hope to find any pockets there, since the pegmatite is very dense, consists mainly of quartz and schorl and has only a bit mica and no garnets, beryl, etc.

But on Sunday, I found some quite large feldspar crystals at two places (attachment:2) and I am wondering, if they could be a sign for a pocket zone… My main concern is that I haven’t found any quartz crystals or a perthite structure yet.

Does anybody have some experience with pockets in this region? Should I start to dig further at the spot where I found the feldspar or are such crystals quite common and ar not necessarily connected with pockets?

Thanks a lot for any helpful comments


Patrick
Attachments:
open | download - tourmaline.jpg (864.8 KB)
open | download - feldspar.JPG (172.8 KB)
avatar Re: Cahuille Mountains: pegmatite pocket?
October 11, 2011 11:19PM
    
Beautiful euhedral crystals like the feldspar shown often are indicative of pockets in pegmatites. Keep looking. You may come up with a bonanza. I envy you. We don't have pegmatites here in western Oregon.
Re: Cahuilla Mountains: pegmatite pocket?
October 12, 2011 04:35AM
Thanks for the answer. I was definitely considering to go again. But I still think that there should be more subhedral quarz xx or mica or clevelandit close to the feldspars or shouldn´t that be the case?
However, no need to envy me. You are obviously close to ome very nice smoky quartz and amethyst crystalls, as I could see on your home page - nice finds.
avatar Re: Cahuille Mountains: pegmatite pocket?
October 16, 2011 11:07AM
    
Patrick,

Based on my experience in the area, if you're not finding euhedral quartz crystals, you're not going to find much otherwise, and those subhedral microclines are very common for the Cahuilla District, which can occur up to several feet across. If you tell me what general area you're prospecting, I may be able to guide you to a more productive location in the district to invest your sweat equity.

Scott
avatar Re: Cahuille Mountains: pegmatite pocket?
October 17, 2011 08:10PM
A little key to help find the pocket, if any do exist(keep in mind that 1/10th of 1% of all pegmatites don't contain pockets)...
...follow the "roadsigns" in many cases the schorl tourmaline are sign post pointing the direction of the highest mineralization. Follow the direction the schorl crystals are pointing. This is a generality and won't apply to all pegs since each is it's own beast but many times the schorl will point towards the areas of higher mineralization. The increasing grain size you are seeing in the larger feldspar crystals is a good sign. Also check for fractures that originate towards the same area or point. Check to see if the fractures have small crystals in them loose or lined. Look for odd bends and attitude changes in the shape of the peg. Any strong upwards trend or downward dips(offsets) indicate a VERY good place for a pocket. Check to see if the country rock drops down into a portion of the peg that is not consistant with the rest of the overall shape. As an example this is a classic example of what happens at Mt. Mica. The best pockets are found where the peg pinches or dips hard in the country rock. Look for spongy otr textural differences in the material. Thats a good indicator. There are a couple other good things but these will help for now
Re: Cahuille Mountains: pegmatite pocket?
October 17, 2011 11:04PM
Scott, Jason

Thanks a lot for the good information. I have just been out again - mainly to dig and get a better overview and to "finish" the site. I could again get some good schorl crystals but have to agree with Scott: the feldspars are here obviously not a sign for pockets. They were like the tourmalines just surrounded by massive quartz. Also, the mineralization was more towards the walls of the pegmatite, whereas the middle part consisted only of massive quartz. However, I am quite pleased with the schorls (I posted one picture on my mindat homepage).
I will keep the "road signs" in my mind for my further field trips and post any success. Well, where would you suggest going then, Scott? So far the Cahuilla Mountains were my favorite spot. I found once a small quartz pocket close to the place where the andalusites are - but nothing really exciting. However, I was also thinking about visiting the area around Little Cahuilla Mountain.
avatar Re: Cahuille Mountains: pegmatite pocket?
October 18, 2011 01:36AM
    
Despite not finding any pockets those schorls are pretty nice, especially since they were won from massive quartz. Best of luck in your search and keep us posted!
avatar Re: Cahuille Mountains: pegmatite pocket?
October 18, 2011 02:35AM
can you post a bunch of pics showing the different features of the peg? Whether anything can be gleaned from them or not is one thing I just like to see pegs in general and live vicariously through the pictures!!!
Keep us up-to-date on your findings and travels.. That schorl are great!
avatar Re: Cahuille Mountains: pegmatite pocket?
October 18, 2011 07:38AM
    
Hi Patrick,

Check out the locality page on mindat for the Sly Rick prospect (Green Centipede claim) Sly Rick prospect (Green Centipede claim) [www.mindat.org]. Also, see my old posts in the forums, which cover directions, etc.

[www.mindat.org]

[www.mindat.org]

Good luck out there.

Scott
Re: Cahuille Mountains: pegmatite pocket?
October 19, 2011 06:20PM
Thanks a lot. So, my next field trip will lead to "dense vegetation consisting of chaparral, which has precluded most exploration activities, especially on the steep north facing slopes".... However, I am still looking forward to it :)

Jason, I didn’t have much good pictures of the schorl pegmatite, since it was just very dirty and mostly covered with soil. But I posted a few pictures from another pegmatite, where I found a small quartz pocket. Perhaps I should spend there also another day or two..

Patrick
Re: Cahuille Mountains: pegmatite pocket?
October 20, 2011 03:14AM
hello im new to pegmatites. i live in cahuilla area and im very interested in local geology. im looking to start hunting in the area can anyone point me in the right direction? books, webs, or just what to look for when im out in the brush. i have done a little research on pegmatites but im more of a hands on kinda guy. im goin to park my jeep around juan diego mine and start lookind from there. any area info or specfics to look for would be great, remember im a rookie first time out,( at least lookin for pegs) i am very familar with the area through ridding, and jeepin. i am active and not affraid to hit the heavy brush on foot or knee whatever it takes. patrick if you are looking for another rig/hunter on your next trip out let me know. actualy that gos for anyone in the area going out on a hunt or wanting to. or anyone already in the area mining. thanks.
avatar Re: Cahuille Mountains: pegmatite pocket?
October 20, 2011 07:55AM
    
Hi Brian,

The Bureau of Land Management and Forest Service have posted the Juan Diego mine area to prevent mineral trespass. Since 2006, visitors to the site have been warned via official signs that any unauthorized removal of mineral materials is prohibited.



Also avoid the Lithia Dike mine, the Audrey Lynn mine, Brian Ward claim, and the Fano mine area, as these are all privately owned. There may be new active claims in the area, so always keep an eye out for monuments, signs, tools and fresh disturbances, and avoid those areas completely. The Sly Rick prospect is likely your best bet, it just requires some strenuous hiking and a little good luck. It's totally worth the effort based on my experience.

Scott
Re: Cahuille Mountains: pegmatite pocket?
October 21, 2011 03:33PM
Hi Brian

If you did already some research on pegmatites, you most likely know the most important facts already. If you keep this knowledge in mind and expand it, e.g. with the "road signs" mentioned from Jason further above you are on a good way.
Now, the trouble is, that in reality things are often more complicated. To make a decision if it is worth to start digging, needs a lot of outdoor experience - and most often one is still at the wrong place.
Basically, any irregularity in the rock or vein is a first good sign, e.g. bulges, unusual big crystals, leached areas, ... Additionally, if you find any mineralized zones with euhedral crystals, you can assume that you are getting closer. And - as Scott mentioned it above - in the Cahuilla Mts. you should find euhedral quartz crystals.
However, I will contact you when I go out for my next trip (perhaps late Nov?).

Good luck until then

Patrick
Re: Cahuille Mountains: pegmatite pocket?
October 22, 2011 12:30AM
Great thanks for the info i will start from the sly mine..yea im a few weeks out my self(puttin a new clutch in the jeep). but yea post when you have a date you think your goin out..thanks again.





Brian.
Re: Cahuille Mountains: pegmatite pocket?
October 22, 2011 11:29PM
"Mineral Materials " is a BLM term that covers non-locatable materials such as sand and gravel. The BLM andf FS do not get involved in removal of minerals from mining claims - that is considered a civil matter. Thus I suspect the sign does not refer to removal of locatable minerals but an attempt to stop unauthorized quarrying. L.Dee, Ex-BLM Geologist
avatar Re: Cahuille Mountains: pegmatite pocket?
October 23, 2011 01:41PM
    
Lawrence,

The Juan Diego mine [www.mindat.org] is on acquired private lands, and all of the hardrock mineral materials on this property are subject to prospecting and leasing via preference rights, which fall under a different set of public land laws than those that address mining claims. The signage for the site has nothing to do with locatable minerals because the land is withdrawn from mineral entry under the general mining laws.

A prospecting permit has already been issued and a lease application has been pending for well over a decade. The mineral estate is managed by the U.S. Department of the Interior, Bureau of Land Management (BLM), and Minerals Management Service (MMS). Surface resources are managed by the U.S. Department of Agriculture, Forest Service.

Mineral trespass at this particular site includes any non-permitted removal of the mineral estate. Call the phone number on the sign if you have any additional questions.

Scott
Re: Cahuille Mountains: pegmatite pocket?
May 25, 2012 12:33AM
You meant to say that the DeSoto mine is on acquired "public" lands, i.e. the BLM or FS acquired them from private sources often by trades. They do fall under a separate and for some reason strange category where a prospecting permit and lease are required to operate on the lands. By going thru the process you acquire the rights to the minerals. In any event neither the BLM or FS would sign the site to curtail locatable mineral trespass - that is the problem of the owner of the mineral rights.
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