Crbiker,
Yeah, I have ridden in gravel pits alot, they can be a lot of fun.
Same thing with sand pits. Before lawsuits were popular we used to have a lot of pits to ride in. One of the cool things is if they are active they are forever changing. Lot of challenging hills and a lot of variety of hills and combinations of.
I have an abandoned gravel pit near my summer cottage. I have been riding there so long that the locals think I own it!
Be sure to set up your suspension for gravel / sand and get a shovel and a rake. You can make some nice berms and jumps with a little work.
Be prepared to go through a bunch of tires though.