I'm not sure. I just found one today though?
What Kind Of Snake Is Black With White Diamonds On Its Back?
Rattle snake
I don't know either. We live in high country Colorado and had one in our yard today. It was about 4 feet in length and quite black with thin white diamond pattern on the back. I could not see any rattles on it.
It might be Black-tailed Rattlesnake.
Is it this one ? 
On the right is a photo of him that I added.
Is it this one ?