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Post by Bob on Feb 21, 2022 14:43:07 GMT -5
One of my friends has rockhounded near the junction of KS, OK, and MO for many years. He has found some extremely heavy concretions--at least that's what he called them--in stream beds from time to time. I held one about the size of an ostrich egg recently and could not believe how heavy it was! He is a photo of one that he put in his yard long ago. What in the world could be the explanation of this heavy weight? I rockhound a lot and knew instantly the rock was extremely heavy for its size.
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Post by hummingbirdstones on Feb 21, 2022 22:15:19 GMT -5
One of my friends has rockhounded near the junction of KS, OK, and MO for many years. He has found some extremely heavy concretions--at least that's what he called them--in stream beds from time to time. I held one about the size of an ostrich egg recently and could not believe how heavy it was! He is a photo of one that he put in his yard long ago. What in the world could be the explanation of this heavy weight? I rockhound a lot and knew instantly the rock was extremely heavy for its size. Cool rock, Bob. The only thing I can think of that makes rocks really heavy is some type of metal content. It's hard to tell from the picture if there's any metal showing on the surface. It looks really washed out.
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rewdownunder
spending too much on rocks
Member since March 2012
Posts: 357
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Post by rewdownunder on Feb 21, 2022 22:27:04 GMT -5
No Idea what that is but a magnet test would be be my first try. Those colors could be related to iron. Has anyone cut one open? Concretions have a internal structure but you have to cut it open to see it.
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,456
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Post by Sabre52 on Feb 21, 2022 22:49:55 GMT -5
Ironstone concretions are super heavy and hard. When I was young, I thought one was a geode and slugged it with a rock hammer. Shot off the hammer like an iron cannonball and conked me on the head, never did that again! *L*
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Post by vegasjames on Feb 21, 2022 22:51:56 GMT -5
The colors do resemble iron compounds.
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Post by rmf on Feb 22, 2022 6:29:16 GMT -5
Sabre52 & vegasjames have nailed it. These are siderite concreations. Some are siderite after pyrite/marcasite. Normally they have other carbonates in as well as the Iron carbonates. These type concretions are common in the Cretaceous sediments of Al, TN, MS. Also the coal areas in KY and IL also have concretions but many of them are filled with pyrite/marcasite but since they have not been on the surface, they have not weathered and tend to be black. If cracked the Pennsylvanian age concreations have visible pyrite. Nodules of Mazon Creek are siderite concretions and they have fossils. Also, Knob Noster, MO concretions also have fossils.
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Post by Bob on Feb 22, 2022 11:11:36 GMT -5
Is the reason for the high weight the marcasite?
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Post by Bob on Feb 22, 2022 17:47:24 GMT -5
He told me that one weighs about 40lbs. He has shown me another one, much smaller, than he cut in half many years ago. Here are pics of the cut side, the natural side, and a cab that he made from it. He claims that it is almost black hematite. When I first saw the cab, I thought it looks like highly polished obsidian, but the moment I held it I knew it was too heavy. In the middle of this one I think I could see a bit of what looked like pyrite.
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realrockhound
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Post by realrockhound on Feb 23, 2022 14:38:09 GMT -5
Ironstone concretions are super heavy and hard. When I was young, I thought one was a geode and slugged it with a rock hammer. Shot off the hammer like an iron cannonball and conked me on the head, never did that again! *L* reminds me of the time I shot one of my hard plastic toy ninja turtles with my BB gun when I was a kid. It ricochet and hit me just under the eye. “You’ll shot your eye out kid” 😂
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