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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).


Glauconite-rich sandstone, Cambrian Bliss Sandstone, west Texas (© 2009

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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