Help me identify this rock, please!

[cyndihaltom02]

This rock was found in Arizona, I believe, about 15 years ago. We are moving to a smaller house and I'm wondering what kind of rock this is as I have not been able to locate a picture of anything like it and I don't just want to toss it because I can't name it. Any information would be greatly appreciated. I have attached several photos for you too look at and hopefully you can help me identify what in the world I have.

 

[Indian Steve]

I would have move that with me! Not sure what it is. I would post this in the Rocks & Gems forum.

 

[TheCannonballGuy]

The semi-transparent center, the "conchoidal" fracturing (the way thick glass will chip), and the white corrosion on the outside indicate that it is one of the many forms of Chert.

Flint is another of the forms of Chert.

I should mention, most Chert is either opaque or only slightly transparent. Your semi-transparent specimen is an uncommon find. It MIGHT have a more-specific name, like Flint is a more-specific name for that variety of Chert.

A Google-search for "chert nodule" turned up the following webpage, with the photo below, showing a (scarce) semi-transparent Chert specimen which looks almost exactly like your first photo.
Chert - Sedimentary Rocks

 

[cyndihaltom02]

On my way to check out the site! I checked the site and I don't see what you are seeing. This rock is probably 14" around X 8" square so it pretty big and heavy. It's multicolored, and I don't see the rock you are telling to me to look for. Perhaps the site I'm on is wrong but I searched for Chert Nodule and it took me to a picture page. I'll try again but I couldn't find the one you were referring to.

 

[cyndihaltom02]

I'm not throwing it away, it is possibly one of the oddest rocks I've ever found and it is huge. The picture does not depict the actual size but it's the size of a football in thickness only rounded. It's very heavy too.

 

[smokeythecat]

It's SiO2. Silicon and oxygen, chert is correct, they are all in the quartz family which includes agate, jasper, chert, amethyst, citrine, smoky quartz, etc.

 

[CaptEsteban]

Chert & some nice flint in it, too ! A VERY nice piece. Looks like it has been used to make tools, also. [ points, scrapers, etc.]

Repost this with pictures on the " Native American Indian Artifacts " forum down the home page, for more expert advice.

 

[TheCannonballGuy]

Clarification:
Cyndi, when I said the rock in the photo I posted shows a (scarce) semi-transparent Chert specimen "which looks almost exactly like yours"... I meant that the mineral looks like yours. The one in the photo has an extremely rough-broken surface, whereas several sides yours have been worn smooth by natural erosion. The "condition" of your chert nodule looks a lot like the ones we find in stony creeks.

 

[tamrock]

A rock of microcrystalline or cryptocrystalline silica crystals that are too small to be seen without high magnification. All good identifications from the above answers IMO and a prized find for a stone age person. May have even been one of those individuals who knocked a few flacks off it long before you found it.

 

[Back-of-the-boat]

Opal? not high quality though.Was it by Ehrenberg Az. if so it could be from Blythe opal mine.

 

[old digger]

I normally associate chert as nontransparent, and your piece looks more like quartz or agate. I find your type of material somewhat plentiful here in Mt.


P.S. Welcome to TNET!

 

[cyndihaltom02]

Thank you for the feedback, it does look similar and you're right the translucent appearance threw me.