> I have mapped it out, read all the posts... I just can't figure out how to get through the tunnel to get the cart. I can't find the sandstone caverns, or the miner with the boulder on his leg. I have the bomb, but it doesn't seem useful for this. Spoilers are great! Please help! All the hints are not doing it for me!

I assume from how you describe it that you're in the right area. When you jump from the mine cart, you have just a few turns to get to where it comes out of the tunnel again. Look for that exit point first (it's the only point further south that you can get to at this point that has rails running by), then find the quickest way to get there after jumping from the mine cart. You'll need to do something else with the pickaxe first.