"No, humans"

As we were walking along in the Norris backbasin (where I was working Thursday), we approached an area with small lodgepole pine trees and a thin soil layer just beyond the thermal features. Cheryl (park geologist, my supervisor) reached down and picked something up.
“Ahh, an obsidian flake”
She was holding a piece of obsidian about the size of a pad of butter. She handed it to me. I haven’t yet visited the obsidian cliffs, so it was the first time I had seen naturally occurring obsidian (outside of a classroom).
“Oh cool,” I said, thinking to myself that it was pretty sharp. Hank (park geologist, Cheryl's husband) had told me earlier in the day that some surgeons actually prefer to use obsidian instead of steel for their scalpels and told a story of slicing his thumb on a piece of obsidian.
“I was just wrenching on the thing, trying to get it out of the ground...then one of the others in the group pointed out that I had blood all over my hand. I had a 1” deep gash cutting right down the center of my thumb. It was the only time I’ve ever had to elevate something. But the doctor told me to keep pressure on it and it would be fine the next day. And damned if the next day that cut hadn’t healed completely.”
I turned to Cheryl and asked, “Was this carried here by water?” We were at least 8 miles from Obsidian Cliff.
“No, humans. I said obsidian flake for a reason”
That blows my mind. And it makes me feel a little giddy inside.