Bob wanted the links put in properly.
Here's the link to the current discussion on Tribe:
http://bm.tribe.net/thread/88266e9d-81a ... c9b87f8c3e
Previous discussions on Tribe:
http://bm.tribe.net/thread/e41af0ad-2bb ... 0cf1946671
http://bm.tribe.net/thread/4ef5347b-43b ... 04d755e768
A fairly detailed post by Ora Uzel:
All of the above harkening back to the link here:
http://www.foresight.org/Conferences/MN ... /Gillett1/
This is from the 42nd annual Graduate Student Colloquium at Penn State:
http://www.geosc.psu.edu/GradColloquia/ ... ct2010.pdf
Gillett's paper does have a semiquantitative mineralogic analysis that looks like this:
quartz - Mj
feldspars - Mj
Micas - Mj
non-silicate minerals - mn
Mj meaning major component, mn meaning minor component. I've seen the exact same thing that was done for my office just recently for shales, using XRD, or X-ray diffraction. The problem with that is you actually need three separate runs to determine the clay mineralogy, if in fact there is any, and you're going to have to separate the materials from each other because the quartz peaks on the diffractogram overrun everything else. Normally some lab technician operating the diffractometer plugs names into the computer based upon what he 'thinks' or is told is there, and then the computer measures the peaks and spits out the results, both in a semiquantitative form and with reproductions of the diffractograms for the individual components superimposed on the main.
To do it RIGHT, you have to have three samples as I previously stated...one for an oven-dry condition, one which has been saturated and then redried, and then one which has been saturated with ethylene glycol, which gives the necessary readings to differentiate whether you're dealing with a 1:1 clay mineral like in the illite group, or a 2:1 clay mineral like in the smectite group. And if you're dealing with mixed-layer clays, then you need more samples to differentiate the components.
Also, Bob, think a minute there. Clays are phyllosilicates (sheet, or layered silicates), just like micas. Separating the two is a royal bitch and a half to make any reasonable determination from the type of the diffractogram that they got.
The problem of differentiating the individual clay minerals (if indeed there are any) in playa dust is worthy of at least a Masters' thesis. I separated all the components in the analysis and then used normative chemistry to figure out what was there based on the geology of the area. Quartz? Absolutely, with a source of the Granite Range. Same for the feldspars and mica. And then it STARTS to get tricky. I did find out one thing though, that there's probably a magnesium sulfate septahydrate out there. Geologists call it 'epsomite'. You know it as epsom salts. And it stands to reason because you're in an evaporitic basin, or you wouldn't have gypsum there. But still, I call that a tentative conclusion and not final.
I haven't had the chance yet to put a slide of playa dust under a polarized light 'scope yet, but believe me, I will.
Now, Emily D:
Yes to the silicone. and make sure you give wiring a generous coat. The first time I went to the playa I started having corrosion problems on the battery of my truck. That was solved using the little anti-corrosive felt rings you can get at an auto parts store for under a couple of dollars.
My research into the dust continues. Fascinating stuff.