heperd 0 Posted August 25, 2011 Share Posted August 25, 2011 I found this when i was a kid around the Chalk Hill -Eagle Ford area of Dallas, which is somewhat famous for that amount of fossils and rock found there. The area was once home to an enormous TDI cement company, so there are many large piles of dirt and rock that have been dug up from hundreds of feet down. Anyway, i just wanted to see what this rock is and if it is anything special. I remember that i broke it open w another rock and found the crystal inside. There are many round rocks like this around the area but ive never seen one w this type of crystal inside. Also you can go 5 feet without seeing a nautilus fossil in this area. Thanks for any help. Jonathan. Link to post Share on other sites
Goldfinger 43 Posted August 25, 2011 Share Posted August 25, 2011 Looks like a geode of some type. Try scratching the crystal with a knife. If it scratches- it's calcite. If not- quartz. My guess is calcite... Interesting find. Your local rock club should have more information on the finds in this area...Steve Link to post Share on other sites
heperd 0 Posted August 25, 2011 Author Share Posted August 25, 2011 Thank you. Link to post Share on other sites
Bedrock Bob 3,891 Posted August 26, 2011 Share Posted August 26, 2011 Looks like calcite. There is a heck of a lot of that stuff in Austin chalk. Nice looking rock!I thought I might add that you mentioned that the property was a big cement company. Well, what you have is the "ore" of cement. Calcite and limestone rich in calcite are the feedstock for portland cement. Link to post Share on other sites
Nugget Shooter 4,610 Posted September 2, 2011 Share Posted September 2, 2011 I agree on the ID and that is one very cool rock! Link to post Share on other sites
xossfs 0 Posted September 9, 2011 Share Posted September 9, 2011 oiuh Link to post Share on other sites
xossfs 0 Posted September 9, 2011 Share Posted September 9, 2011 this is a serpintine nodule. It was a clay ball being gently rolled around on a mud flat by wave action. the mud ball then drys out slowly and cracks internally from the volume loss of the water. Then the dried mud ball is deeply buried and the cracked inside is filled with Calcite crystals. The one that I have has a brown calcite druze with creamy yello dog tooth calcit crystals sitting up on top if the druze. Link to post Share on other sites
Nugget Shooter 4,610 Posted September 11, 2011 Share Posted September 11, 2011 Again I say very cool and thanks for a clearer ID Link to post Share on other sites
Goldfinger 43 Posted September 12, 2011 Share Posted September 12, 2011 this is a serpintine nodule.I disagree with the serpintine (sic) nodule. I think you mean septarian.http://en.wikipedia....erpentine_grouphttp://en.wikipedia....ian_concretionsReally nice find though regardless.Steve Link to post Share on other sites
Nugget Shooter 4,610 Posted September 13, 2011 Share Posted September 13, 2011 OK learning here sooooooo? Link to post Share on other sites
Bedrock Bob 3,891 Posted September 13, 2011 Share Posted September 13, 2011 I disagree with the serpintine (sic) nodule. I think you mean septarian.http://en.wikipedia....erpentine_grouphttp://en.wikipedia....ian_concretionsReally nice find though regardless.SteveSeptarian nodule. I dont think so. Neither is it sepentine from my understanding of the word. Septarians are a whole lot like my Moqui Marbles. I have a few with fossils. I will post some photos this evening.Calcite for sure. But what you would call the "nodule" I could not say. It looks exactly like the deposits of calcite in S. New Mexico. We have them 20 feet in diameter filled up with that dog tooth calcite and banded in all colors. A lot like geodes but huge. Link to post Share on other sites
Goldfinger 43 Posted September 14, 2011 Share Posted September 14, 2011 I agree it's not a septarian nodule... Definitely not serpentine either.Steve Link to post Share on other sites
Bedrock Bob 3,891 Posted September 14, 2011 Share Posted September 14, 2011 I just spoke to a friend that runs a concrete plant. He calls that nodule a "dogger" or "calcrete". He says that these nodules were formed as calcite leached through a calcium/magnesium rich strata. They are found in and below layers of old sea bed where the soluable minerals concentrate. He says that calcite bedded in layers is generally called "calcrete" and that calcite formed in nodules is called a "dogger". It is the common formaiton of calcite in a bedded formation.Septarians are very different and it is a mystery how they were formed, although they can have calcite crystals. Serpentine is an ore of asbestos and looks completely different... Link to post Share on other sites
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