I just joined the group, and it looks like a great place for me to learn about rocks and minerals. I enjoy collecting them, but my knowledge of what I'm collecting is pretty minimal.
With that said, I have posted some photos of some pieces of what I'll call geodes in the Yellow Cat, Utah area. They are relatively small spheres when whole- about 1.5 - 2.0 inches in diameter.
I'm curious what these are and what the different layers are. The outside of most of them is a rough brown color. Then there's the red layer, sometimes banded. Then there's a clearish layer that either has a surface of small crystals or a bubbly surface. Then as you can see in the photos, there is sometimes a central "core" of a brownish material. If you expand the photos, you'll be able to see the texture of the central part.
I'm also curious how these form- if it's a series of periods with liquids filling a cavity with different minerals that precipitate out?
I'll get some photos of other rocks I picked up there, as I'll have questions on those too. Yellow Cat is definitely an interesting place with a huge variety of things to look for. I've still nt found any of the red wood limb casts.