philfort Posted July 13, 2003 Share Posted July 13, 2003 Just curious... can someone explain what causes these weird starbursts and shards in these rocks? Quote Link to comment Share on other sites More sharing options...
E-rock Posted July 13, 2003 Share Posted July 13, 2003 ... Quote Link to comment Share on other sites More sharing options...
fern Posted July 13, 2003 Share Posted July 13, 2003 I think those are porphyritic. the starbursts are phenocrysts ... crystals that froze out of the magma at depth while the background matrix was still molten. At a later time and shallower depth the background darker rock mass froze quickly into a much finer grained texture. but then I am not a geologist. Maybe I should limit my comments to ..."oooo pretty!" ... where did you find these? Quote Link to comment Share on other sites More sharing options...
philfort Posted July 13, 2003 Author Share Posted July 13, 2003 (edited) "The rock (of Mt Thompson) is andesite of the Naches Formation, typical of the region." ... so says Beckey. This is in the scree below the peak. We didn't see any of these rocks on the peak itself, but there were a lot mixed in in the talus. Here's as good a closeup as I have: We hypothesized that they were snowflake fossils Well, anyway, I thought it looked cool... Edited July 13, 2003 by philfort Quote Link to comment Share on other sites More sharing options...
E-rock Posted July 13, 2003 Share Posted July 13, 2003 Ooops, hehe, Fern's right! I'm deleting my bullshit now. Quote Link to comment Share on other sites More sharing options...
fern Posted July 13, 2003 Share Posted July 13, 2003 Quote Link to comment Share on other sites More sharing options...
lummox Posted July 14, 2003 Share Posted July 14, 2003 philfort said: Just curious... can someone explain what causes these weird starbursts and shards in these rocks? god. leave it at that. Quote Link to comment Share on other sites More sharing options...
iain Posted July 14, 2003 Share Posted July 14, 2003 fossilized druggie needles, hope you wore gloves Quote Link to comment Share on other sites More sharing options...
iain Posted July 14, 2003 Share Posted July 14, 2003 the phenocrysts look like feldspar, the darker pink variety having an increased potassium content while the whiter ones lean more to the calcic side of things. cool rock! Quote Link to comment Share on other sites More sharing options...
Alpinfox Posted July 14, 2003 Share Posted July 14, 2003 Phil, I remember seeing those things up around Mt. T. You didn't climb that chosspile did you? My second took a fall on the W. ridge due to a broken hold which pulled me through a tree and off my belay stance. Scraped/bruised me up pretty good and taught me to keep my toprope belay tight or to belay off the anchor. Then on rapping the descent, a rock hit my partner in the arm and she couldn't feel it for two days... Anyway, I hope you had a better outing on it than I did. Quote Link to comment Share on other sites More sharing options...
philfort Posted July 14, 2003 Author Share Posted July 14, 2003 I didn't find the rock that bad. Of course, if I'd had an experience like you, then I'd probably label it a chosspile too. Thanks for making the route more solid. The worst part was the sketchy scree on the descent. Quote Link to comment Share on other sites More sharing options...
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