There's a landscape supply ie: rocks of all kinds, in SW Denver that sells it by the 15lb bag if ya know of someone coming your way from here.
I was working along RR tracks in UT this summer and found a bunch of it free for the pickin up, but didn't want to check it in my luggage
Huntsman, I bet you get a good burn from that once it gets goin, pretty hard to get started up high.
