Mike,

Thanks for the new info. The first thing you should probably do is find

out where the nearest 13 million year old volcanic bedrock is to the area

where you found your sample. A geologic map of Texas, or someone at the

local university or survey, should be able to provide you with this. What

you're looking for is a Miocene-age volcanic field, of which there are

several in the Texas-New Mexico area. The other thing is to get a major

element analysis to classify the rock. I can't remember if you already

did this, but it's another test you can get done commercially, probably

for under $50. Since it's very fine-grained, you would need that to tell

if it's an andesite, dacite, rhyolite etc.

We have the thin section, but the groundmass is so fine grained that it's

difficult to interpret textures. I am scheduled to analyze a bunch of

"unknowns" that people have sent us (you're not the only one) on the

electron microprobe later this month. That should tell us more about its

chemical makeup. If I do the full calibration (which we usually only do

for publication-quality meteorite analyses), I could conceivably get you

something close to a major element analysis (we don't do sample fusions

here, but it's so fine-grained that a broad beam analysis will probably

approximate it's bulk-rock composition).

Sorry I haven't been more responsive, but our various government-funded

research projects all have deadlines. I haven't even had a chance to

open the package you sent me over a month ago. We do this other work

really out of pure interest and the kindness of our own hearts. If you

decide to tell other people your latest findings, that's fine. Just

remember, we (that is, the UofA) haven't gone on record with what we think

this rock is yet, and that's the way we'd like to keep it until we find

out more.

cheers,

Jamie Gleason

******************************************************************

James D. Gleason

Lunar and Planetary Laboratory

University of Arizona

Tucson, AZ 85721

(520) 621-7984 (phone)

(520) 621-6783 (fax)

jgleason@gamma1.LPL.arizona.edu