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Offline markus

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Need help identifying a rock
« on: 05/02/2009 08:28:10 »
Hi, I would really like some help in figuring out what this piece of rock is. It is a rather light, and has some pink, red and orange to it. Any help would be _much_ appreciated. Also, I don't know if you an see it in the picture, but up close the rock appears to be made of a rough inner core of sorts, with a thinner, sort of bubbled and multi-coloured outer layer.


 

Offline Karen W.

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« Reply #1 on: 05/02/2009 09:40:08 »
hmmmm I wonder if the rock at one time contained gas or air bubbles when formed maybe it was liquid at some point.... Jim Bob or Bass.. will be able to give it a shot I am sure.. I know nothing but am curious.. It looks really familiar to me.. I have seen similar sometime long ago around here..but I think it may have been something from a collection I viewed at a show...
 

Offline Bass

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« Reply #2 on: 05/02/2009 22:10:03 »
can you get any better pictures- none of these appear in focus on my computer?  Based on your description, my first guess would be gossan- the weathered remains of ore deposits.  My second guess would be some sort of volcanic rock, like pumice.  But can't see the pictures well enough to distinguish.
 

Offline markus

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« Reply #3 on: 05/02/2009 23:39:40 »
Sorry about the image quality, I only have a very crappy old digital camera at my disposal, but I will see if I can take some better shots. I was also thinking some sort of volcanic rock because of the surface, but I don't know. If you hold a very bright light source behind it, you can actually see through the outer layer a little, like when you hold your fingers in front of a lamp. The colours I can see all seem to be sort of different coloured cloudy regions below the surface. Here are my new pictures.

newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/01.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/02.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/03.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/04.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/05.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/06.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/07.JPG [nonactive]
 

Offline Bass

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Need help identifying a rock
« Reply #4 on: 06/02/2009 01:04:03 »
Looks more volcanic in those pictures.  See if you can borrow a better camera and get more detailed shots- that would really help
 

Offline markus

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« Reply #5 on: 06/02/2009 01:11:33 »
I will try and get another camera asap. In the meantime, are there many volcanic rocks that are somewhat transparent? Is there any other way I can help you to figure what it might be? Also, what can I use to clean a rock like this? Near impossible to get the dirt out of all the little dents.
 

Offline Karen W.

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Need help identifying a rock
« Reply #6 on: 06/02/2009 02:05:09 »
can you get any better pictures- none of these appear in focus on my computer?  Based on your description, my first guess would be gossan- the weathered remains of ore deposits.  My second guess would be some sort of volcanic rock, like pumice.  But can't see the pictures well enough to distinguish.

Pumice.. That is what looks like!

Then My mother used to buy this weird yard decorating rock that looked just like that too.. it was very light weight.. not heavy per say... I wonder if that is what it was.. I thought it was pumice?
 

Offline Karen W.

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Need help identifying a rock
« Reply #7 on: 06/02/2009 02:05:37 »
The colors would be right also!
 

Offline Karen W.

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Need help identifying a rock
« Reply #8 on: 06/02/2009 02:08:17 »
Do you have one that is already split open somewhere..?to see the inside... Please don't split one.. just wondering what the inside is like?
 

Offline markus

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« Reply #9 on: 06/02/2009 02:38:24 »
This is my only sample, I have never seen another one. I have several pieces of pumice here, and they roughly the same outside texture with the hundreds of bubble like marks. But in between the bubble, this rock is smooth, unlike my pumice samples that are all jagged and rough. The weight of this rock is a fair bit heavier then my pumice pieces of an even larger size, but is still fairly light for rock. As i have tried to explain, it appears to consist of two layers, an outer, semitransparent almost glassy layer, and then rough red kinda ordinary core. The pictures I have been able to take do not do justice to all the colours it has, at one point it is a sort of blood red, but at another it is a kinda sickly orange yellow mix, with lots of odd shades and colours in between. If i had to make a guess as to how this rock was formed, i would say that a piece of the boring red material was somehow encased in a molten form of the outer material. But yeah, i'm no expert.
 

Offline markus

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« Reply #10 on: 06/02/2009 03:15:45 »
Here are a few more pics:

newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/08.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/09.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/10.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/11.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/12.JPG [nonactive]
 

Offline Karen W.

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Need help identifying a rock
« Reply #11 on: 06/02/2009 04:04:47 »
number 1 and 3 are way to dark to see!
 

Offline Bass

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« Reply #12 on: 06/02/2009 04:26:09 »
Your description, plus all the photos, make me suspect my original guess, gossan, may be right.  Gossans typically form where there are enough sulfide materials to generate sulfuric acid, which leaches most of the rock except the most resistant, which is silica and iron oxides.  I'll continue to wait for some better photos before a final verdict
 

Offline markus

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« Reply #13 on: 06/02/2009 04:58:51 »
That makes a fair bit of sense, chemicals eating away at the outer layer would definitely explain much of the surface. Do you know anyway I could confirm this idea? And could you explain how this may have resulted in such a light weight? Thank you all very much for the help so far, I am getting my hands on a much better camera in about 4 hrs, so I'll be uploading some more soon.
 

Offline markus

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« Reply #14 on: 07/02/2009 02:13:18 »
Here we go, these are a lot better

newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/1.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/2.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/3.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/4.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/5.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/6.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/7.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/8.JPG [nonactive]
newbielink:http://www.starnaudsc.vic.edu.au/home/mcraigie/9.JPG [nonactive]
 

Offline Karen W.

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« Reply #15 on: 07/02/2009 02:34:36 »
Much Better piccy's!!!

Excellent!

I change my opinion....

That looks like it could have a certain amount of quartz around the outer surface and that the insides are different for sure...

Very curious what bass says or Jimbob..
 

Offline Bass

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« Reply #16 on: 07/02/2009 19:46:46 »
As Karen said, better photos.

I stand by my last opinion.  The outside is cryptocrystalline (very fine-grained) quartz- I would call it jasper.  JimBob would probably call it chert- because he sees considerably more chert as a soft-rocker, and I see considerably more jasper in the fun rocks.

Photo 2, 4, 5:  Pitted jasper.  The pits may have been some sort of rock fragment, zeolite or sulfide mineral that weathered out.

Photo 3, 8:  Photo 8 is by far the best photo.  It clearly shows gossan (iron oxides) in the center, even some possible fine-grained sulfides in quartz at the top, and quartz veins going through the interior.  This probably formed as a metallic sulfide (like pyrite) - quartz deposit that was deeply weathered.  As the sulfide weathers, it forms sulfuric acid, which leaches (destroys) the remaining rock, which is then replaced by low-temperature jasperoid.  Iron oxides and silica are resistant to weathering, and will be the last remnants remaining.  Looks like this piece was then tumbled in a streambed, where it was rounded and the less resistant fragments were picked out, leaving the pockmarked appearance.  Had the interior been almost anything else (instead of silica-iron oxides), I probably would have called it a chert nodule.



Can I ask where you found this (I would guess desert or semi-arid environment)?
« Last Edit: 07/02/2009 19:58:18 by Bass »
 

Offline Chemistry4me

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« Reply #17 on: 07/04/2009 07:05:08 »
Anyone know what this is? Why does it look like it has cotton balls growing on it?

 

Offline Bass

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« Reply #18 on: 07/04/2009 16:49:40 »
Possibly zeolites? Scolecite?

Zeolites are hydrated (K,Ca,Na)aluminum silicates.  The crystal structure allows zeolites to absorb all sorts of compounds, making them useful in all sorts of industry applications, including environmental remediation.
 

Offline JimBob

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« Reply #19 on: 07/04/2009 17:01:07 »
BASS!! PLEASE - It is a fossilized clam that had tumors

OK  - that isn't true - it is still close to April 1 and I am a very mentally ill person.

This is a geode - http://en.wikipedia.org/wiki/Geode (see the 4th picture down on the right side and enlarge it by clicking on it.)

The round moth ball looking thingies are actually small clumps of quartz crystals that are very small.

============================================================

============================================================

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And I have a different interpretation of this - I was coughing my lungs out when this was posted last month - very sever case of bronchitis had just started.

This looks like blast or impact ejecta glass. The rind is a product of the heating of the rock as are the pits.
 

Offline JimBob

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« Reply #20 on: 07/04/2009 20:05:38 »
OK - after a bit of searching in between a tad bit of work, here are pictures of impact ejecta.

All are in the class of stuff called tektites - a good definition of which I have not been able to find.

All were produced by a meteorite impact and ejected from the impact crater.

Wen I first started in school in geology, tektites were mysterious glass forms that no one had any idea how they were formed. There are numerous numbers of these here in central Texas, especially just on top of soils formed from the Cretaceous limestones. These turn out to be from the K-T boundary impact event in the Yucatan.

The ones below are from all over the world.





Note the iron rind











This picture also has rinds on some of the ejecta
 

Offline Bass

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« Reply #21 on: 07/04/2009 20:36:21 »
REJECTA the EJECTA! ;D

I stick by my original answer.
 

Offline JimBob

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« Reply #22 on: 08/04/2009 00:46:06 »
REJECTA the EJECTA! ;D

I stick by my original answer.


Ignorance is bliss!

We shall have to differ on this one. And I will continue to look for other similar rocks.

http://www.minersoc.org/pages/Archive-MM/Volume_25/25-161-82.pdf
This is a very interesting reference from 1938 - it even mentions the theory that the moon came from being torn from the area of the Pacific Ocean.
 

Offline quirkly

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« Reply #23 on: 14/05/2009 22:31:25 »
Looks like an amygdule that has been somewhat reworked. I have found similar rox in Oregon and N. NV.

From a volcanic terrane?
 

Offline JimBob

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« Reply #24 on: 17/05/2009 05:35:13 »
Baas, I suspect that you are rather familiar with the field geology of this area - intimately involved (BUT NOT BIBLICALLY.)  Whattaya think? Ever seen ejecta like this?

I have seen ejecta rinds on core volcanic bombs from Raton Volcano New Mexico with feature similar to this.

It is still eject!
 

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« Reply #24 on: 17/05/2009 05:35:13 »

 

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