thair Posted October 21, 2010 Share Posted October 21, 2010 This was found by a friend on the Brady Creek in Mills Co. Central Texas. Just thought it was real neat due to the unusual preservation. Lots of caves in this part of the world so it was probally eroded out of one of them then deposited in the creek. Crystals apear to be quartz. Link to comment Share on other sites More sharing options...
Terry Dactyll Posted October 21, 2010 Share Posted October 21, 2010 thair.... Thats really nice, the crystals make it even more special... Cheers Steve... And Welcome if your a New Member... Link to comment Share on other sites More sharing options...
thair Posted October 21, 2010 Author Share Posted October 21, 2010 This was found by a friend on the Brady Creek in Mills Co. Central Texas. Just thought it was real neat due to the unusual preservation. Lots of caves in this part of the world so it was probally eroded out of one of them then deposited in the creek. Crystals apear to be quartz. Sorry I forgot to put size. It is about the size of a softball, fist size. Link to comment Share on other sites More sharing options...
barefootgirl Posted October 21, 2010 Share Posted October 21, 2010 Mineral and fossil specimens together are my favorite! Thank you so much for sharing that with us. In formal logic, a contradiction is the signal of defeat: but in the evolution of real knowledge, it marks the first step in progress toward victory. Alfred North Whithead 'Don't worry about the world coming to an end today. It's already tomorrow in Australia!' Link to comment Share on other sites More sharing options...
fossiladdict Posted October 21, 2010 Share Posted October 21, 2010 Well it's pretty cool. Looks like quartz to me as well. Fossils are simply one of the coolest things on earth--discovering them is just marvelous! Makes you all giddy inside! Link to comment Share on other sites More sharing options...
Auspex Posted October 22, 2010 Share Posted October 22, 2010 Neat looking, for sure. Wonder whether it might be a septarian nodule that didn't quite "get off the ground"? "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...
MikeD Posted October 22, 2010 Share Posted October 22, 2010 That's a strange one. Cool! Link to comment Share on other sites More sharing options...
JimB88 Posted October 22, 2010 Share Posted October 22, 2010 More than likely calcite crystals which formed during erosion (like flowstone) Quartz is an igneous rock and is not associated with fossils. Quartz can form and often does form in water, but its usually geothermally heated and too acidic for limestone or dolostone to survive. Some calcite crystals get very large and are formed by hydro dissolution and precipitation (in other words rain dissolves the calcite as it passes through the limestone and then deposits it in cavities (and fossils.) Still a very good specimen. Link to comment Share on other sites More sharing options...
Shamalama Posted October 22, 2010 Share Posted October 22, 2010 (edited) More than likely calcite crystals which formed during erosion (like flowstone) Quartz is an igneous rock and is not associated with fossils. Quartz can form and often does form in water, but its usually geothermally heated and too acidic for limestone or dolostone to survive. Some calcite crystals get very large and are formed by hydro dissolution and precipitation (in other words rain dissolves the calcite as it passes through the limestone and then deposits it in cavities (and fossils.) Still a very good specimen. Actually I have to disagree with you on several points. First: Quartz is a mineral, not a rock and it is indeed associated with fossils. Many fossils are found "Silicified" where Quartz has replaced the original shell, organic material, or crystalline material. Obvious examples are Petrified wood, Agatized Coral and Beekmanite. Heck, there is a whole range of minerals that have been pseudomorphed (chemically replaced but structurally preserved) by Quartz. Second: Quartz does "form in" water, it dissolves in and precipitates out from water. You are correct that Hydrothermal fluids are the primary carrier but those fluids are not always acidic to the point of wholesale dissolution of limestone. Otherwise you wouldn't have silicified fossils found in limestone such as those found in the Jeffersonville limestone around Kentucky or the Permian fossils from the Glass Mountains in Texas. Third: Calcite can form from Hydrothermal fluids just like quartz. It is the temperature, composition (what elements are dissolved in the fluid) and pressure of the fluid that determines what mineral is deposited. Meteoric water (rain) will dissolve small amounts of Calcite (Calcium Carbonate) and redeposit it as flowstone while moving through the ground, but crystals generally form with supersaturated fluids that remain in place for long periods of time. Edited October 22, 2010 by Shamalama 1 -Dave __________________________________________________ Geologists on the whole are inconsistent drivers. When a roadcut presents itself, they tend to lurch and weave. To them, the roadcut is a portal, a fragment of a regional story, a proscenium arch that leads their imaginations into the earth and through the surrounding terrain. - John McPheeIf I'm going to drive safely, I can't do geology. - John McPheeCheck out my Blog for more fossils I've found: http://viewsofthemahantango.blogspot.com/ Link to comment Share on other sites More sharing options...
Wrangellian Posted November 10, 2010 Share Posted November 10, 2010 Actually I have to disagree with you on several points. First: Quartz is a mineral, not a rock and it is indeed associated with fossils. Many fossils are found "Silicified" where Quartz has replaced the original shell, organic material, or crystalline material. Obvious examples are Petrified wood, Agatized Coral and Beekmanite. Heck, there is a whole range of minerals that have been pseudomorphed (chemically replaced but structurally preserved) by Quartz. Second: Quartz does "form in" water, it dissolves in and precipitates out from water. You are correct that Hydrothermal fluids are the primary carrier but those fluids are not always acidic to the point of wholesale dissolution of limestone. Otherwise you wouldn't have silicified fossils found in limestone such as those found in the Jeffersonville limestone around Kentucky or the Permian fossils from the Glass Mountains in Texas. Third: Calcite can form from Hydrothermal fluids just like quartz. It is the temperature, composition (what elements are dissolved in the fluid) and pressure of the fluid that determines what mineral is deposited. Meteoric water (rain) will dissolve small amounts of Calcite (Calcium Carbonate) and redeposit it as flowstone while moving through the ground, but crystals generally form with supersaturated fluids that remain in place for long periods of time. I've had to educate at least one otherwise-knowledgeable fossil guy on that point about quartz not only being found in igneous rock - here on Vancouver Island we have shale with seams of quartz (he thought calcite) running thru it from tectonic/hydrothermal activity, and we find fossils and 'Herkimer diamonds' (quartz) in the same outcrops... much as in Herkimer NY, I imagine. I think the xls in the pic are quartz just by the look of them. 1 Link to comment Share on other sites More sharing options...
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