Complex sentence: The sandstone is a medium grained variety, and was originally light gray, however, the mica and clay in the rock oxidizes and turns a tan color, although not all of Chatsworth Formation has oxidizes, and some is still light gray.
Split into simpler sentences: The sandstone is a medium grained variety, and was originally light gray, however, the mica and clay in the rock oxidizes and turns a tan color. Not all of Chatsworth Formation has oxidized yet, and some is still light gray.