When viewed closely, most pieces of coal are composed of alternating bands of bright and dull material. Image by West Virginia Geological and Economic Survey.

Geology.com has an interesting article about coal.   Here in Illinois, we have a huge amount of it.  Most, if not all, is from the Pennsylvanian and is closely associated with Mazon Creek fossils.  Next time you’re out hunting for fossils and you come across a lump of coal.  Have a closer look and appreciate the hidden beauty of coal!