Please help identify this interesting rock!

[pebbles2]

I'm new to this forum. Does anyone know what this rock is? The middle looks quartz, and at the edge is blue. When held to the light or sunlight the blue turns to an amber color. Any help appreciated!

[Kane]

Location is essential.

[ynot]

This is  cross section of an agate nodule.

[Ludwigia]

I agree. An extremely weathered one.

[pebbles2]

Thank you very much guys! Appreciate you shedding some light on this. It was in a box with a few other rocks, stored in an old barn in the upper Midwest for over 4 decades. I will try to upload pictures of the other rocks. When you say it's been weathered, do you think it a good /bad idea to try to polish it? Or just keep it how it is? It's  a little heavy and about 8" or so in diameter. Thanks!

[Ludwigia]

51 minutes ago, pebbles2 said:

Thank you very much guys! Appreciate you shedding some light on this. It was in a box with a few other rocks, stored in an old barn in the upper Midwest for over 4 decades. I will try to upload pictures of the other rocks. When you say it's been weathered, do you think it a good /bad idea to try to polish it? Or just keep it how it is? It's  a little heavy and about 8" or so in diameter. Thanks!

 

It looks somewhat fragile to me and could easily crack open while trying to grind it flat in my opinion, so I'd leave it as is.

[v100v]

Looks awesome 

[pebbles2]

Thank you very much all of you guys! It's very much appreciated! I just made another discovery about this. Each side of the blue agate?  outline is a bit different in shape. I would think a cross section would be the same on each side. I also tested it with white and yellow light bulbs, as well as the above mentioned Sun. Each time, the blue disappears, and a yellow hue shines through in every situation (so far). I forgot to mention earlier, it's heavy, about 7 to 8 lbs. at least. Again, thank you all for helping me discover more about this mystery rock.

 

p.s. As I mentioned this rock came in a box with a few other rocks. I'll try to upload pictures of them shortly. Here's one I had a chance to take some pictures of. I did some research. Here were my original thoughts....blue opal, sieber blue agate. Honestly, I'm new....I'm not sure. Any thoughts?

 

 

 

[DPS Ammonite]

34 minutes ago, pebbles2 said:

Here were my original thoughts....blue opal, sieber blue agate. Honestly, I'm new....I'm not sure. Any thoughts?

They are pieces of glass or glassy slag. Note the large and smalll bubbles that are not found in natural opal, agate or chalcedonies.

[ynot]

Agree with glass chunk for the blue piece.

[Fossildude19]

2 hours ago, pebbles2 said:

Each side of the blue agate?  outline is a bit different in shape. I would think a cross section would be the same on each side.

 

Not necessarily. These minerals leach into the rock, and can narrow down, or widen out, as the rock allows.

[ynot]

2 hours ago, pebbles2 said:

Each side of the blue agate?  outline is a bit different in shape.

Very few agate nodules are symmetrical.

[pebbles2]

I want to thank you all for your responses. This has been truly educational. This has made me appreciate nature more and more. Again, I just want to say thank you!

[pebbles2]

Hi again guys! Here is another rock that was in the box with this collection. I have no clue what it is. I tried to look online. I've got nothing so far. Thanks!

[ynot]

Another agate piece.

[daves64]

Banded agate that formed around multiple lumps & nodules in the host cavity that have since eroded away. The cavities are rarely, if ever, smooth inside.

[pebbles2]

Thank you guys for all of the information! I learned a lot. The most important piece I'm interested in is the first rock. Based on what I understand, this is a cross section of an agate nodule. I would like to understand what's behind the color changing when exposed to the light. Why the blue is disappearing when exposed to light. If anyone can shed some light on this, it would be much appreciated!

 

p.s. here is the last rock in the collection...as I said this collection has been stored for over 40 years. I would like to know what I have before putting them back in storage. Thank you!

[ynot]

Last one looks like a metamorphic quartz rich sedimentary rock.

[daves64]

3 hours ago, pebbles2 said:

I would like to understand what's behind the color changing when exposed to the light. Why the blue is disappearing when exposed to light. If anyone can shed some light on this, it would be much appreciated.

That is due to light reflection. Light from the front is being reflected back at you in the blue range, while from the back it's just shining through the stone, showing more of the lights hue. I live in Ellensburg Wa where we have the rare Ellensburg Blue agate. I have one stone that with reflected light, looks like a blue, but shining light through the back show's it to be what's generally called a "smoke" agate. It literally turns a whitish gray.

[pebbles2]

Thank you! Much appreciated!