need a closeup shot por favor. It's chert at first glance. basically fossilized sea goo that solidified and silicified. Is it worth anything? Well that depends on if you want to make some arrowheads, or if you broke it up into chunks and put them in a rock tumbler you would get some sweet stones. Good weathered chert can be used for a variety of jewelry and crafts.
could be goethite, second photo shows what looks like precipitate formations. This one still thinks it's chert though, it has all the hallmarks. It would look BA if you had it sliced (it would be very difficult though) into coasters or maybe even a cheese plate. If you sold it whole you wouldn't get as much for it as you would if it was processed into workable sizes.