Yea, Denver is awesome for tar...really good, really cheap, and even easier to find, although the open air went more underground when i left a few months ago (but by then i had a delivery service bringing balls to my house every day so it didnt matter)
If by powder you mean china though, then there is none to be found...there is "powder" that i found (the best shit i had done out there too), but it was brown/almost reddish in color with dark brown rocks mixed in..cooked up that nice clear amber in the rig...