What Type Of Rock Is This?

[everyday user]

Anyone know what this orange rock is? There were a few scattered along this cliff I found. They seemed to be at the same layer height but spread out. It looks like they formed first then the grey rock formed around them? The cliff is in a cove where a waterfall used to be millions of years ago. The cove is in Massachusetts if that helps.

[everyday user]

[jasong]

A concretion or nodule. You'd have to see what sort of material the yellow rock is, the gray appears to be shale.

Concretions are usually derived from minerals in the country rock. Nodules are replacement features that can be totally different than the country rock. They are used somewhat interchangeably since the line can blur. If they are chert I'd call them a nodule since that's a replacement mineral. If they are ironstone/limonite then I'd call it a concretion since they usually precipitate and don't replace. I'd lean towards a concretion since it appears to have grown. 

Knock one open with a hammer, might be something in the middle.