Rockpervert Posted March 15, 2011 Share Posted March 15, 2011 I've been wracking my brains trying to think what it is about the chemistry of these rocks that causes the classic white colouration of St. Clair plant matter, but come up resoundingly empty-handed. Any suggestions...? Thanks Gethin Certifiably one trilobite short of a Silurian picnic... http://fossil-world.lefora.com/ Link to comment Share on other sites More sharing options...
Fossildude19 Posted March 15, 2011 Share Posted March 15, 2011 My link Regards Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
Rockpervert Posted March 16, 2011 Author Share Posted March 16, 2011 My link Regards I'd never have guessed Aluminium silicate. Thanks for that, Fossildude! Certifiably one trilobite short of a Silurian picnic... http://fossil-world.lefora.com/ Link to comment Share on other sites More sharing options...
grand8228 Posted April 1, 2011 Share Posted April 1, 2011 The white colored minerals in fern fossils at St. Clair, PA are primarily pyrophyllite (Al2Si4O10(OH)2) with minor kaolinite (Al2Si2O5(OH)4). The pyrophyllite probably formed under low temperature metamorphic conditions (about 275 degrees Celsius, or 525F). The coal at St. Clair is anthracite, which forms at temperatures greater than ca. 250oC. The ferns died during the Pennsylvanian age (about 310 million years ago) and were buried under up to 8 km of sediments and rock. During burial, the area was heated to 250 to 300 degrees C, allowing pyrophyllite to form. Few coals were buried as deeply or exposed to as high temperatures as those in eastern Pennsylvania, so the presence of pyrophyllite is unusual. Pyrophyllite does occur occasionally in other coal beds around the world but not in such striking fossil remains. Link to comment Share on other sites More sharing options...
Auspex Posted April 1, 2011 Share Posted April 1, 2011 Great information, grand8228; thank you! (And welcome to the Forum) "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
flyguy784 Posted April 3, 2011 Share Posted April 3, 2011 Great explanation, thanks. Link to comment Share on other sites More sharing options...
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