ErikAndere Posted March 28, 2021 Share Posted March 28, 2021 Folks on mindat.com suggested asking this question here! This is less of a "what is this a fossil of" question and more of a "is this possible" question. I have a small chip of translucent chalcedony showing a mass of white inclusions, two of which look very much like a grass seed-head. The gist of the conversation so far has been 'is it possible for fossil material to be an inclusion within a silica mineral like agate or chalcedony?' As opposed to an agate-replacement or opal-replacement fossil like an agate limb cast, agatized wood or agatized/jasperized opaque mudstone with intact fossil imprints of leaves and fish. Because pseudo-fossils in chalcedony are so common, with organic-appearing moss, dendrites and "garden" quartz mislabeled as fossil material all the time, there is a knee-jerk reaction of "never." But, am wondering... is it mechanically impossible or just highly uncommon? It has been suggested it may have formed in association with a mineral-rich hot spring, first as opal, then as agate. This was found in the John Day basin, Antelope/Ashwood area of central Oregon, in a drainage downslope from a 15-square mile basin that is ringed with lahar palisade formations (think Clarno palisades from John Day Nat. Monument.) The area has standing agatized tree trunks 5 feet high and 2 feet thick, and is full of smaller petrified wood and plant fossils. Age is 30-40 million years, in an overlap between John Day and Clarno formations. Private property, with permission. Apologies for the quality of the photos, am taking pictures with a phone through a hand lens. Link to comment Share on other sites More sharing options...
Fossildude19 Posted March 28, 2021 Share Posted March 28, 2021 Cropped, contrasted, and enlarged: 1 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...
FossilDAWG Posted March 28, 2021 Share Posted March 28, 2021 There are certainly examples of plants being preserved in chert deposited in silica-rich hot springs. One example is the Princeton chert in the Allenby Formation (Eocene) near Princeton BC. Another would be the Ryne Chert (Devonian) from Scotland. That chert is opaque and the fossils, preserved at the cellular level, are revealed by cutting thin sections. I can't think of examples right off, but it seems possible that plants and other fossils could be preserved in translucent silica deposited in a hot springs type of environment. Don 3 Link to comment Share on other sites More sharing options...
fossilcrazee Posted March 28, 2021 Share Posted March 28, 2021 That is way cool ... I would be dancing to find that! Link to comment Share on other sites More sharing options...
ErikAndere Posted March 28, 2021 Author Share Posted March 28, 2021 Thanks for the response! I will keep an eye out for more. Link to comment Share on other sites More sharing options...
Top Trilo Posted March 29, 2021 Share Posted March 29, 2021 I have a piece of polished chalcedony and always assumed fossils couldn't be preserved in it so the inclusions were mineral but are you saying there is a chance it is biologic? “If fossils are not "boggling" your mind then you are simply not doing it right” -Ken (digit) "No fossil is garbage, it´s just not completely preserved” -Franz (FranzBernhard) "With hammer in hand, the open horizon of time, and dear friends by my side, what can we not accomplish together?" -Kane (Kane) "We are in a way conquering time, reuniting members of a long lost family" -Quincy (Opabinia Blues) "I loved reading the trip reports, I loved the sharing, I loved the educational aspect, I loved the humor. It felt like home. It still does" -Mike (Pagurus) “The best deal I ever got was getting accepted as a member on The Fossil Forum. Not only got an invaluable pool of knowledge, but gained a loving family as well.” -Doren (caldigger) "it really is nice, to visit the oasis that is TFF" -Tim (fossildude19) "Life's Good! -Adam (Tidgy's Dad) Link to comment Share on other sites More sharing options...
ErikAndere Posted March 29, 2021 Author Share Posted March 29, 2021 2 hours ago, Top Trilo said: I have a piece of polished chalcedony and always assumed fossils couldn't be preserved in it so the inclusions were mineral but are you saying there is a chance it is biologic? Apparently! But still, with the huge range of minerals that can very closely mimic organic forms, mineral may be the much more likely. With sizable quartz crystals being lab-grown in decent quantity right now, seems likely someone's experimented with it. The temperature & pressure conditions inside an autoclave used for developing lab-grown quartz are probably hostile to any kind of organic matter, but if it is first encased in opal or a lower-temperature silica deposit, maybe it could be demonstrated to survive the process! 1 Link to comment Share on other sites More sharing options...
Sjfriend Posted March 30, 2021 Share Posted March 30, 2021 I am NOT a geology major but I would think with the heat that is usually associated with quartz / agate formation I would question the chances of organic material surviving. Chert is commonly found with fossils but I've not found organics just shell types (shells and crinoids). That being said that 2nd piece sure looks like a great seed. Link to comment Share on other sites More sharing options...
DPS Ammonite Posted March 30, 2021 Share Posted March 30, 2021 41 minutes ago, Sjfriend said: I am NOT a geology major but I would think with the heat that is usually associated with quartz / agate formation I would question the chances of organic material surviving. Chert is commonly found with fossils but I've not found organics just shell types (shells and crinoids). That being said that 2nd piece sure looks like a great seed. Agate and quartz (and opal) can form near the surface at low temperatures. Silicified plant material is common. Here are some reeds in agate. They probably were opalized at one time. 1 1 My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
ErikAndere Posted April 1, 2021 Author Share Posted April 1, 2021 The same formation produces some really nice agate-replacement wood as well. This is a cross-cut, photographed wet; the specks are pyrite cubes. 1 Link to comment Share on other sites More sharing options...
Recommended Posts