Not Your Everyday Agates, Help ID Types & How Formed?

[MyGodMagma]

Here are 3 bizarre agates in my collection, all from the same small creek bed where I regularly find Paleozoic fossils and lovely druzy chunks of agate. These 3 are atypical finds, and I'm wondering if anyone can shed some light as to what type of agates they are, or provide me with the proper descriptive words to be able to learn more about them. I'm also VERY curious as to how these are formed, as the two agates without the quartz seem to bloom in an outwards fashion; all of my other agates appear to all come from geodes. Anything would be helpful, really, I've tried to research them myself and come away with more questions than answers. I think I'd have more luck if I knew the proper way to describe them in a search query. Thanks~caroline

 

The second pic is of the backside of these agates. 

 

[izak_]

I know nothing about agates, so I can't help, but those look awesome!

[Doctor Mud]

This looks like Botryoidal agate or Botryoidal Chalcedony.

 

Botryoidal habits form out of clusters of spheres. This could happen when minerals form around a nucleus (grain of sand for example) and then the cluster fused together.

[ynot]

Agate is a cryptocrystalline quartz. This means that a whole bunch of really small crystals are laid down over each other in layers. Any other minerals that are laid down with the quartz will cause colors to the layer. 

The pieces You have can be called "banded" or "fortification" agate.

Chalcedony is a white to clear type of agate.

Some areas will build up faster than other areas leading to the rounded lumpy nature of the surface. This type of surface is called botryoidal and is a common feature of agates.

Sometimes the crystals will keep growing and become visible to the naked eye, and form a druse on the surface. This can be covered by subsequent layers of agate.

The pieces You have  are stream tumbled and have had the high points worn down to expose the layers underneath and made them look like bulls eyes.

 

Green is an unusual color for agate.

[PaleoRon]

They are of a type commonly referred to as Crowley Ridge agates. They can be found in a fairly widespread area in Louisiana and Mississippi and possibly other states. Most of the specimens I found in Mississippi were of a yellow to tan color, but I also found a couple that were grey and one that was pink/red.