Experts, please ID this find

[mope540]

Found this while hunting for arrowheads in a dry creek bed. Grabbed it because i figured that it would look good in the aquarium. It's somewhat translucent in the thin area (as seen in the pic), and measures roughly 2" x 2 1/2".
Thanks for any help!!!

 

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[Bajahunter]

It appears to be an amygdule of Chalcedony. That is quartz that cooled off too rapidly to form large crystals.
Should have a hardness of around 7, a white streak, and concoidal fracture.
Here is a picture of one I found. Mine hasn't been broken open yet. It is about the size of an egg.

 

[Tigger]

Wow, too neat for the fishes. I love how you can see both the smooth exterior and the crystals inside. Great display specimen!

 

[mope540]

It appears to be an amygdule of Chalcedony. That is quartz that cooled off too rapidly to form large crystals.
Should have a hardness of around 7, a white streak, and concoidal fracture.
Here is a picture of one I found. Mine hasn't been broken open yet. It is about the size of an egg.

Thanks a lot for your expert opinion, Bajahunter...and thanks for the pic too. Mine is also about the size of an egg. I added pics from slightly different angles to get a better view of the crystals
Thanks, Tigger. the fish will now have to wait for a different rock.

 

[Bajahunter]

Mope
Thanks for the extra pictures. Mine is mostly hollow, very light. Yours is much more filled in. Could more correctly be called a geode.
I still think it is chalcedony outside but probably quartz inside. Are the crystals well formed, regardless of size, or are they more rounded or lumpy.
Definitely an interesting specimen.
New pictures are the bottom of my "egg" showing the light coming through. The two other Chaledony geodes, showing mamalarian (breast shaped) form and botryoidal (cluster of grapes) form.
Rob

 

[mope540]

Mope
Thanks for the extra pictures. Mine is mostly hollow, very light. Yours is much more filled in. Could more correctly be called a geode.
I still think it is chalcedony outside but probably quartz inside. Are the crystals well formed, regardless of size, or are they more rounded or lumpy.
Definitely an interesting specimen.
New pictures are the bottom of my "egg" showing the light coming through. The two other Chaledony geodes, showing mamalarian (breast shaped) form and botryoidal (cluster of grapes) form.
Rob

Rob
Some of the chrystals further inside have facets and come to sharp points. Some of the outer ones still have facets, but most are rounded...i imagine from wear and tear due to the many years sitting in a creek?.?.
I have ordered a cheap digital microscope camera, mainly to take pics of coins, but when it arrives i'll have to try it on this rock to get more detailed pics.
Thanks for the info, and the pics

 

[mope540]

Rob, here are some close ups. some of the crystals look almost like cut stones

 

[Twisted One]

I used to keep fresh water and salt water reef tanks, and I would highly suggest if intending to put that in a fresh water tank with fish to soak it, and boil it first, and I am afraid I am not sure what boiling it will do to the crystals if anything. But any chemicals, natural or otherwise that was in that stream at one time will be in that crystal too.
Not too mention it was probably from a volcanic region at one point meaning it might also contain sulfur in it.

Sulfur, Iron, and 99% of the chemicals probably used to mine in that area would be unhealthy to any aquarium setting, and will most likely leach from crevices and pores in that rock.

I learned the hard way when I killed a couple of $60 Discus, I bought a rather nice quartz piece from a local flea market guy that said it was a great aquarium piece. I assumed he meant it was already cleaned and been used before....I was wrong.

And if it is a salt water tank, don't put it in it! Even cleaned, it only take of almost anything to throw off the balance.

 

[olroy70]

I am going to have to look over this forum closely.

I have found numerous rocks in Indian campgrounds that I have dragged home over the years.
I, like the indians, have an eye for the beauty of them. Think they carried em home for the kids or themselves!

olroy

 

[StoneWhisper]

Agreed.. Well worn but broken Chalcedony (Thunder Egg)