This is a science kit from the Smithsonian with 6 different science activities for kids. My daughters started with the Dino Dig activity. In the box is a sandish block with basic chiseling tools. Inside the sandish block are dinosaur "fossils" and one has to chisel them out.
My daughters took turns and started digging away. This is not an activity to be finished in a few minutes as it requires careful chiseling to avoid damaging the mock fossils inside. Eventually they found something.
A "fossil"!!! My kids thought this was cool and spent the next 2 hours digging away. They found other fossils, but not enough to complete the full dinosaur. In fact, they still have quite a bit to go.
They loved working on this and remained focused the whole time! This is a great activity to occupy your kids for an afternoon, but I'll warn you that if you do this in the house as we did, dust from the chiseling gets everywhere in the immediate location.