I saw at the MineExpo back in the early 90's a water jet, proposed to cut slot shaped blast holes. I may even have the info on it out in a box in the garage still?. At those big Mine shows you see all kinds of stuff that looks good, but never really takes off. Traditional mining methods still remain for the most part the way to do it, just the machinery get more advanced. Continuous type mining machines have made more headway in the hardrock mines within the last 30 or so years, but those are really only cost effective where the ground condition are of low compressive strength and softness. This is a rig of one of my customers they use to carve out huge heading, such as subway and highway tunnels. I've sold cap-lamps to outfits that use a smaller rig such as these to carve out wine cellars in the Napa valley. As far as I could tell of the water-jet machine I saw, it looked like it would work in some applications. It really didn't consume a great deal of water either, but excess water in the work area can be solved with a pump. A pneumatic diaphragm pump is the best for that. Funny I just called my other branch to have a 2" diaphragm pump to be sent to my house this morning. I don't think we'll ever stop thinking of new found methods to dig in rock without explosives as that's the future imo, heck I even saw a rock router concept once. It was the same idea as a wood router, but bigger and it could cut square tunnels, oval tunnels, round or what ever shape of tunnel you could think of. I have some ideas in my head now on some possible methods, but I'm more of a dreamer then a man of great ambitions. I'm often called easy money by all the folks I deal with. As for actual mining I've been there done that, Drilled, shot, mucked, bolt and hung wire, drove crib raises, concrete, shotcrete, and timbered, that's a young mans job, but it ain't like it was 40 years ago. Now a miner can listen to his IPod, eat a sandwich and move levers all at ones on a Drill Jumbo and be able to drillout as much as three 12'x12'x16' headings in a 12 hour shift... Fun part of my job is still going underground at so many places over the years it's hard to recall them all now. So many of them have shut down or been mined out over the years.