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Mineral name?


Malone

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Hi

wondering if there is a name for this reddish mineral combination that I see frequently in per-mineralized fossils? I found a couple pictures to use as examples. 

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Red color usually comes from iron oxide elements in the matrix. 

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Yes, especially the powdery yellow/ orange coating of many triliobite fossils such as those found from the Cambrian and Ordovician of Morocco is limonite. 

This is an iron oxide-hydroxide and often occurs when the original trilobite body is attacked by bacteria after death, specifically sulfur producing anaerobic bacteria. Iron in the sediments reacts with the sulphur to form iron sulfide and this is set upon by aerobic bacteria causing the oxidation to pyrite. This then "rusts" to form the limonite coating. 

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On 2/18/2018 at 8:45 AM, Tidgy's Dad said:

Yes, especially the powdery yellow/ orange coating of many triliobite fossils such as those found from the Cambrian and Ordovician of Morocco is limonite. 

This is an iron oxide-hydroxide and often occurs when the original trilobite body is attacked by bacteria after death, specifically sulfur producing anaerobic bacteria. Iron in the sediments reacts with the sulphur to form iron sulfide and this is set upon by aerobic bacteria causing the oxidation to pyrite. This then "rusts" to form the limonite coating. 

Thank you! That is very informative!

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