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top showing hole with crystals formed
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I am very curious about this petrified muscle.  It was found in Mt Ida Arkansas.  I attached pictures and hope u can tell me about it.  It has crystals formed on the inside .


First off, the term is mussel, not muscle.

You don't say what formation you collected it from in the Ida area.  It could be from either Mississippian or  Pennsylvanian aged shale rocks.  If you found it weathered out of the rocks and did not have to chip it out, it was probably form the Mississipian aged shale.  The crystals inside the shell were more than likely deposited by diagenesis.  This is a process that takes place in sediment buried to great depth.  The sediment is under the great pressure of burial, at high temperature.  Over time certain elements like silica become mobile dissolving out of the shells of some buried benthonic organisms incorporated in the sediments.  These elements move in aqueous solution as ions and over time with the right condiditons, can coem together form crystals.  In this case, in the void in the shell.

What you have is a mussel probably preserved in a shale.  It looks more like a mullusk which is heavy enought to weather the compaction of the shale.  I cannot say, just from looking, but sometimes the shell material, the calcium carbonate is replaced by another mineral.  This might explain the crystal overgrowths inside the void of the shell.  If the crystals are softer than quartz, that is harder than 7 on the mohs scale and will scratch glass, then they are quartz if they are softer then they are another mineral.


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Keith Patton


I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.


I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.

American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing

Bachelor and Master of Science
Registered Geologist in State of Texas

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