Sunday, March 2, 2008

Pacific Silica Quarry

I have neither died nor fallen into the ocean, though it kind of feels like the latter, considering how I feel like I'm frantically doggy-paddling to keep afloat in all the reading, composition, thesis writing, rehearsals, performances, and occasional field trips.

The field trips, of course, are the fun part. My mineralogy class has gone on two in the past week, to vastly different but equally interesting places. I'll address these in two separate photo-heavy posts.

Last week's trip was to Pacific Silica Quarry in Perris, California. It has been long abandoned in terms of industrial purposes, but it's still open to anyone who wants to traverse very uneven, cracked, muddy, and hilly roads (the TA drove - the professor seemed pretty terrified) in search of minerals. The quarry taps into what seems to be a pretty big granitic pegmatite (far far bigger than the ones I mentioned in the Box Springs - those were only a couple of inches wide). It has all of the expected minerals for such a formation, with the added bonus of large schorl tourmaline crystals cutting across the quartz and feldspar.



It also had some particularly interesting formations of biotite, in long narrow strips criscrossing the quartz and feldspar of the quarry walls in shapes that are reminiscent of Chinese calligraphy.


While there were a few assigned questions for the trip (mostly in the form of finding specific things and drawing them), a large portion of the time was allotted to simply looking around for interesting things. And, if I do say so myself, I think I did pretty well for finding interesting things. I found two big chunks of euhedral k-feldspar - neither is the entire crystal, but one has five very clear crystal faces, and the other has what appears to be an enormous carlsbad twin. I also found a piece of quartz with a bunch of angular impressions in it that were obviously caused by k-spar crystals growing up against the quartz. Nobody else found any feldspar samples comparable to these, so I felt pretty awesome about it. They are now sitting very proudly on my desk.


Here's the one with five clear faces. For some reason, though, it did not want to be photographed without blur.

And here's the one with the big twin. I haven't seen that narrow crystal face on any of the feldspar we've looked at in the lab.


This is the dented quartz. This picture shows only the biggest imprint, but there are a bunch of smaller ones on the underside of the sample.

Our TA found some tiny garnets on a piece of feldspar, and when we looked closer, we found a bunch more stuck in or next to the tourmaline. Though garnet is not weird for pegmatites, it apparently has not been documented in this particular pegmatite before - there was no mention of it on the USGS map we had for the site, and the professor said she hadn't come across mention of them after years of reading up on the area in preparation for taking mineralogy classes there. She encouraged us to contact the USGS about what we found. (I think she's a fantastic teacher, and stuff like this is one of the reasons. She gets students excited to find things, and holds up that what we do find is significant beyond the scope of a grade in a class.)

A non-mineralogical thing that made me excited about this site was the view. Standing at the top of the hill into which the quarry was blasted, one is afforded an amazing view, from the San Gabriel Mountains down to Mt. San Jacinto. It's a much wider and less-polluted view than from the Box Springs. I loved being able to follow the such long sections of the paths of the San Andreas and San Jacinto Faults by tracing my finger in the air along prominent features (complete with scribbly circle thing upon hitting Mt. San Gorgonio).



We also had excellent weather timing. It was clear the entire time we were poking around in the quarry, but started to drizzle as soon as we got back in the vehicle. Half an hour earlier and we might have missed the garnets, but it held out just as long as we needed.

3 comments:

Tuff Cookie said...

Wow - those are some of the coolest mineral pictures I've ever seen. I know my mineralogy prof would be absolutely salivating over some of those crystals.

Good luck with the thesis - I went through approximately the same panic stage about this time last year for my senior honors thesis. You'll survive! (I did, but only by the grace of a large supply of Thin Mints and liberal application of margaritas afterward.)

Silver Fox said...

How large are those tourmaline xtls, anyway - and those are spectacular photos.

Julian said...

Tuff Cookie: Thanks, both regarding the photos and the thesis! I'm actually on track to finish the draft of the prose thesis this weekend (though I still have a whole composition thesis for next quarter...), and candy has been a huge survival tool for the process. Since you have reminded me that it's Girl Scout Cookie season, I may have to take your Thin Mints suggestion...

Silver Fox: If you look closely, there's a pen for scale in the tourmaline photo; I realize in retrospect that it was not the best scale to use, since it's basically the same color as the outcrop. The largest of the tourmaline crystals in that photo are at least four inches wide, if not five. I took a piece home that is three and a half inches wide (though only about an inch and a half thick - hard to extract elongated ones!), and there were even bigger ones elsewhere in the outcrop.
Glad you like the photos!