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 Post subject: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 6:13 am 
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I would like to know what stone this is so if anyone can identify it - Big Thanks :)
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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 1:06 pm 
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I suspect it is a reddish chert. This rock is common in the Franciscan Complex, along coastal California.
In the case of the red chert found on our coastline, the reddish tone is the result of a small proportion of iron rich deep-sea clay, the very finest sediment that settles to the seafloor far off shore. Due to geosynclinal uplifting the chert rises to form very large outcrops here.

Anyone else have a thought?


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 3:42 pm 
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oh wow thank you, that was very informative!
it feels very dense and quite heavy but with a close look you can see its layers upon layers:
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quite beautiful when it's wet like reddish brown color:
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I think you might be right here :)


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 6:46 pm 
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Barbra Voltaire wrote:
I suspect it is a reddish chert. This rock is common in the Franciscan Complex, along coastal California.
In the case of the red chert found on our coastline, the reddish tone is the result of a small proportion of iron rich deep-sea clay, the very finest sediment that settles to the seafloor far off shore. Due to geosynclinal uplifting the chert rises to form very large outcrops here.

Anyone else have a thought?


Spot on Barbra, this type of chert was used extensively by native americans for arrow/spear heads.


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 7:15 pm 
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I was going to say,"jasper", but then ran across this:
https://www.mindat.org/mesg-7-245968.html
Check out the comments section as it's a funny collection of rock nerds arguing over a name. Good thing gemologists don't do that. :lol:

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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 8:22 pm 
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That is funny.
As a geologist, I would call chert: chert.
As a rock hound (especially if I put a polish on my chert) it would become jasper. :wink:

Outcrops of chert are not in short supply on the California coast.
Here's a beauty! Look at those folds. Wowza.
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Ancient deep ocean siliceous ooze deposits preserved as ribbon chert in the Franciscan Formation (Jurassic age), Marin Headlands, CA


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 05, 2017 10:31 pm 
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Yeah, the whole chert/flint/jasper/agate/chalcedony nomenclature issue takes on different meanings in different contexts and gets really messy really quickly. Best to sidestep it entirely in most cases.

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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Thu Jul 06, 2017 8:20 am 
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so if polished it will become a big shiny jasper?
any idea how much it would lose from its size and weight by making it a Jasper?
I believe it weighs around the 10kg.
would you recommend doing so?
Thanks


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 12, 2017 5:23 pm 
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Where is it from? If Arizona, it might be jasperized wood.


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Wed Jul 12, 2017 5:44 pm 
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dchallener wrote:
Where is it from? If Arizona, it might be jasperized wood.


or chertized wood?
or agatized wood?

:mrgreen:


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Thu Jul 13, 2017 1:04 pm 
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I think that the cost of cutting would be greater than the value of the jasper.
http://www.firemountaingems.com/itemdetails/H201572CB


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 Post subject: Re: Can Anyone Identify This Rock?
PostPosted: Fri Jul 21, 2017 3:49 am 
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dchallener wrote:
Where is it from? If Arizona, it might be jasperized wood.


It's was actually found in Israel at the mid 70 I believe in the "Eilat Mountains".
we kind of like it the way it is I just wondered how much it would lose from its size by sending it to polish.


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