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Post by Jugglerguy on Jul 18, 2012 18:19:32 GMT -5
I went to the beach to pick up some fossils today and found a fossil with crystals in it. Here's a typical fossil I picked up: Here's the crystal fossil: Here's the edge where the crystals are: A little closer: The fossils are limestone. Any idea what the crystals could be?
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Jul 18, 2012 19:11:24 GMT -5
The first thing to rule out of course would be calcite. How soft are they?
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Post by Jugglerguy on Jul 18, 2012 20:51:45 GMT -5
I understand the concept of doing a hardness test, but I've never done one. According to what I just read on a website, calcite has a hardness of 3. A fingernail is about 2.5 and a penny is about 3. If I can scratch it with a penny, but not my nail, it's a hardness of about 3. The problem I have is that the crystals are very small. A penny is huge in comparison. I could probably find a piece of copper wire around somewhere, but even that is pretty big.
I also have some muriatic acid in the garage. Calcite would react with acid.
There's also a calcite mine about 45 minutes north of here, so calcite is in the area. Do calcite and limestone normally occur together?
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Minnesota Daniel
freely admits to licking rocks
A COUPLE LAKERS
Member since August 2011
Posts: 891
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Post by Minnesota Daniel on Jul 19, 2012 20:15:39 GMT -5
Limestone is calcite. Just like sandstone is quartz.
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jason12x12
freely admits to licking rocks
Member since October 2011
Posts: 798
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Post by jason12x12 on Jul 19, 2012 21:51:09 GMT -5
selenite possibly
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Post by paulshiroma on Jul 19, 2012 21:59:18 GMT -5
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Post by Jugglerguy on Jul 19, 2012 22:37:49 GMT -5
My wife, the middle school science teacher, just explained to me the "limestone is calcite" statement. I'm still trying to figure out the difference between a rock and a mineral. So calcite is a mineral and the rock limestone is made of it. Got it.
I still haven't done a hardness test. I'll do that tomorrow. I'll read up on barite and selenite tonight.
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Post by Jugglerguy on Jul 20, 2012 18:57:15 GMT -5
I was able to scratch it with a piece of copper electrical wire. I couldn't scratch it with my fingernail. It reacted with muriatic acid. I read the selenite does not react with acid, but I couldn't find anything about barite. My guess is that it's probably calcite. Thanks for the help!
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