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Post by grumpybill on Sept 13, 2017 17:23:31 GMT -5
My 10 year old grandson found this while we were digging through the rock pile at a local rock shop. I'm new to rock identification (outside of building stone), so I'm looking for assistance in IDing this critter. Top.JPG:  Side:  Edge:  Back:  If better photos are needed, I'll use my macro lens and try again. |
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Post by MrMike on Sept 13, 2017 18:10:29 GMT -5
Coral
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Post by grumpybill on Sept 13, 2017 19:14:19 GMT -5
Thanks.
Fossilized? A file skates on the smoother edges without leaving marks.
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Post by vegasjames on Sept 13, 2017 20:14:51 GMT -5
Definitely coral but not fossilized. It is bleached.
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Post by MrMike on Sept 13, 2017 20:16:13 GMT -5
Must be silicified if a file won't bite into it. This means the calcium carbonate skeleton of the coral has been replaced by silicates thus fossilized.
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Post by vegasjames on Sept 13, 2017 20:27:46 GMT -5
Must be silicified if a file won't bite into it. This means the calcium carbonate skeleton of the coral has been replaced by silicates thus fossilized. I disagree that it is fossilized. If it were fossilized then the pores of the coral would also have filled in and it would be very unlikely to be that white. In some cases fossils form in limestone that can be removed by acid exposing more of the silicated structure. But do to the attraction between calcium and silica again the pores would have also been filled in with silica during the silification process. The other way to tell would be to put a drop of acid on the coral. If it were fossilized then no fizzing will occur. If it fizzes then it is still unfosilized calcium carbonate. |
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Post by MrMike on Sept 13, 2017 20:50:57 GMT -5
Must be silicified if a file won't bite into it. This means the calcium carbonate skeleton of the coral has been replaced by silicates thus fossilized. I disagree that it is fossilized. If it were fossilized then the pores of the coral would also have filled in and it would be very unlikely to be that white. In some cases fossils form in limestone that can be removed by acid exposing more of the silicated structure. But do to the attraction between calcium and silica again the pores would have also been filled in with silica during the silification process. The other way to tell would be to put a drop of acid on the coral. If it were fossilized then no fizzing will occur. If it fizzes then it is still unfosilized calcium carbonate. Agreed |
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Post by coloradocliff on Sept 13, 2017 23:46:26 GMT -5
We all learned something here. Thanks guys, and especially Jim.
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Post by grumpybill on Sept 14, 2017 5:10:25 GMT -5
Thank you, gentlemen.
When the grandson pulled it out of the pile, my first thought was coral. But...I've always thought of coral as soft/brittle (my only prior experience with coral is finding it on beaches); it passed the knife test; and it was buried in a pile of pet wood and other hard rock, making me think maybe my initial ID was wrong.
I doubted it was fossilized because there isn't any sort of buildup between the "fins".
Then, after we got it home and the file skated, I began to wonder if it was some sort of crystal formation. Hence, my asking the experts here.
I'll hit it with a drop of acid after the sun comes up, for shits and giggles, then let the kid give it to his mother for her fish tank.
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