Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: mia531 on 12/10/2012 14:49:22
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FOUND THESE STONES ON A BEACH IN PANAMA. These stones have the white rock either as a layer towards the surface or as a filling in the middle. Some of the associated rock ( eg piece in foreground has lilac milky rock-what is that?) has an orange colour and orange or orangey pink crystals-what is the orange ? What is the white stuff, it is very dense and very white and smooth and hard. Hope someone can help?!
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Red Chert (https://commons.wikimedia.org/wiki/File:The_Childrens_Museum_of_Indianapolis_-_Wyandotte_chert_nodule_-_detail.jpg) ? ...
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http://blogs.agu.org/mountainbeltway/2010/11/03/tavsanli-zone-part-5/
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I think RD is probably right about the red-chert (jasper if you prefer), which would make the white stuff quartz. The hardness is going to be diagnostic; it needs to be about 7. If it's only about 4-5, you could have limestone/marble. Go for it with a knife. :)
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looks like typical vesicle filling and volcanic breccia cemented with chalcedony. white is opal/chalcedondy (very fine grained quartz), I suspect the red is rhyolite or silicified rhyolite.
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No arguments from me, Bass; unless it's softish. I used to have a specimen that looked very much like the large one in RD's post, but I could scratch it with a knife, and it fizzed a bit in warm HCl.
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Thank you all again for your responses.I have attached a close up photo as I'm not sure that the white resembles quartz...The solid white rock is very smooth and opaque. I looked up rhyolite which seems to be very granulated and unlike my sample...
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My monitor is giving me problems today, but it looks like banded agate or chalcedony as mentioned before.
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I think you are right to rule out rhyolite, although it is not always granular. Obsidian is an amorphous form of rhyolite that is a natural glass. However, it’s hardness is rarely greater than 5.5, so, unless you can scratch your specimen with a piece of quartz, it’s not obsidian. Of course, Bass mentions silicified rhyolite; I’m not going to try to argue with that, except, perhaps to mention Ockham’s Razor. :)
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I agree that the top one in the second post looks somewhat like chalcedony. I say this due to the "border" that goes around the outer edge.