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Post by renny1 on Aug 7, 2012 10:18:31 GMT -5
Found on lake shore, 150+ pounds. Grooves are 3 inches deep and 4 inches across and go all the way around. Any Ideas? Coral maybe? Attachments:
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Post by kap on Aug 7, 2012 11:37:18 GMT -5
Sandstone?
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Post by renny1 on Aug 7, 2012 13:20:28 GMT -5
never heard of sandstone around here, eastern South Dakota, but could be I guess. It is a very hard rock
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Post by justarock on Aug 7, 2012 20:26:55 GMT -5
(?) Rhyolite (>69 % SiO2), could look like sandstone. The Yellowstone eruptions dumped a lot in that area. In the past 2 million yrs (3 eruptions), it has ejected over 3700 cubic kilometers.
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Post by mikeyrocks on Aug 8, 2012 16:51:57 GMT -5
Most fossilized coral has a repeated pattern often snowflake, starlike, or pentagonal shaped of various sizes. Highly agatised is considered the best material. This does not appear to be that.
The cuts in this that you mention suggest glacial movement.
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Post by renny1 on Aug 8, 2012 20:27:07 GMT -5
You are right, no agate at all, and glacial activity is what I hoped it wasn't. Cool rock though, every one that sees it has to walk over and look at it. Thanks for your thoughts.
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