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Happy St. Patrick’s Day Rock (repost)

March 17, 2009

Yeah, I know … St. Paddy’s Day is more of an American holiday than an Irish one … blah blah blah, etc., and so on … whatever, it’s fun!!

Because I am really lazy busy I am going to re-post my green rock from last year’s St. Patrick’s Day.

This photo is from the Cambrian Bliss Sandstone in the Franklin Mountains of westernmost Texas. The greenish material is glauconite … an authigenic mineral that typically forms in marine shelf settings, thought to reflect very slow sedimentation rates. In this example, the glauconitic sandstone is actually reworked material (note the cross stratification).

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Glauconite-rich sandstone, Cambrian Bliss Sandstone, west Texas (© 2009 clasticdetritus.com)

To learn more about what glauconite actually is, how it precipitates in sedimentary rocks, and what it means, check out this paper from Chavez and Reid (2000; Sedimentary Geology, v. 136)

Happy St. Patrick’s Day!

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