UGR Sighting (Unidentified Green Rock) Can you help?

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Offline Spencer

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I've shown this rock to a number of geologists (working a drill site) and all just shook their heads.  It was found along the Oregon Coast near Tillamook.  I thought I was being a good citizen and retreiving a crumpled plastic grocery sack from the surf.  It's about 5 inches in length and 3 high.  The bottom appears to be slate, the remainder is various shades of green, mixed along lines and fractures. Any help identifying it would be appreciated. It's much admired and I'm tired of telling people I've no idea what it is!
[attachment=626]

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Offline JimBob

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #1 on: 04/09/2007 23:52:26 »
Spencer if all of the rock is sedimentary then you are looking at a rock originally shale, then got dried out, probably someplace else, and mud cracks formed. this is the curly stuff, mud that has dried out and curled up some. Then I would guess water returned in a flood, mixed up the mud clasts and later - if the line in the upper left is a contact - had sand deposited on top of it.

Thats the best I can do without more information.

The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline JimBob

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #2 on: 05/09/2007 00:29:23 »
By the way:
WELCOME TO THE FORUM!
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline Spencer

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #3 on: 05/09/2007 14:55:57 »
The upper portions of the rock, (above the grey) are very 'glassy' and have conchoidal fractures. It's quite dense.  (Wish my newly ordered scale would arrive!) One amateur collector suggested it might be chrysoprase?
And Thank you for the welcome!
Spencer

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Offline Bass

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #4 on: 05/09/2007 17:44:13 »
Hard to tell from the photo, but the color does not match the chrysoprase that I've seen- which is more of an "apple" green.  My guess would be agate or jasper (cryptocrystalline quartz).  Agate can appear in a variety of colors and is common along the Oregon coast.
Nice specimen.
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Slow enough to study rocks
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Offline Spencer

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #5 on: 05/09/2007 17:56:33 »
Makes sense.  The beach I was combing is renowned for agates.  I'm just used to picking up the more translucent, yellow to red variety.  I did some photo comparisons with green agate and jasper and at least for now, lean toward agate.  Thanks for the input, Bass.

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Offline Bored chemist

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #6 on: 05/09/2007 19:28:32 »
The only "rock" I have ever seen that looked like that was furnace slag.
Any steel smelting in the area?
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Offline Spencer

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #7 on: 05/09/2007 19:43:14 »
Not that I can determine.  However, I do happen to work with a former steel mill operator, and he said it's "too pretty" and doesn't look like any slag he's ever seen.  Thanks for the idea!

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Offline Bass

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #8 on: 05/09/2007 23:56:45 »
Also, slag wouldn't be attached to layered rock
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Offline JimBob

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #9 on: 06/09/2007 01:13:44 »
Now that I know more I am on Bass's side. But unless they are conchoidal fractures in the upper right then it is agate that has possibly the result of the replacement of mud cracks - just a suggestion, but they look very suspiciously like them to me.
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline tedstruk

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #10 on: 13/03/2008 23:40:33 »
Try this (FREE!!!):  It is my lithic evaluation online form to field identify minerals in the field... [:D] They call it layered
newbielink:http://www.toledotel.com/~ope/salepics/FMIndexA/lithicID.htm#submit1 [nonactive]

Looks like a dinosaur head....

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Offline JimBob

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #11 on: 14/03/2008 00:12:43 »
It is most defiantly NOT a dinosaur head. No teeth, muscle or nerve foramen, or even teeth or tooth sockets. How do you get from an altered sedimentary rock to a dinosaur????????
The mind is like a parachute. It works best when open.  -- A. Einstein

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Offline Bass

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UGR Sighting (Unidentified Green Rock) Can you help?
« Reply #12 on: 14/03/2008 01:01:30 »
I stand by my previous answer
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub