Re: Quartz Origins (Uh-Oh, Another Geology Post)

Joe wrote:
OK, I finally got some photos up. Find 'em here:
http://profile.imageshack.us/user/jgandalf/

The site puts them in the reverse order to what I would expect, so
start with the right hand picture. The leftmost is a photomicrograph
of the area under the text box on the previous pic. FOV here is about
2 cm.

Did I do OK?

Joe

Pictures look fine. Did you try the muriatic acid yet? OR scratching it with a pocketknife?

Superficially, the two closest things the photos look like are a quartz (?) version of the chert cryptozooan reef structures we have around here (Cambrian, early Ordovician in age) or some sort of wormtrack structures eroded out of limestone (very close in morphology) and then silicified, although how I'm not sure this could happen. Or my first guess-- weird slag. Do you have any idea what the age of nearby rocks are?

Definitely looks more like quartz than calcite.
Wish photos 3 and 4 were larger. Photo 5 looks like limestone where the quarter is, and silica elsewhere, so I would test both for fizzy. Trouble is, this mix of chemistry may occur both in an algal reef structure which is partly silicified or chertified, and you guessed it, in slag with part glassy and part hardened flux (limestone.) What is the reddish stuff in the pockets like? Have you taken a magnet to the rock, to check for magnetic iron?
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