random about how and when we find them. No plan or scheme to it. We've picked them up over many years. We just look at them and decide to pick them up. Two of our favorites are a rock that one of our "family" picked up on a trek when we were a Ma & Pa, shaped exactly like a heart. They picked it up and gave it to us. Some kind of igneous rock.
Another one is one I found while out geocaching with some friends. It's a piece of basalt about 16 inches tall shaped exactly like a capital "L" — about 8 inches long on the bottom side and about 4 1/2 inches in width and thickness. It's perfectly symmetrical. I had to pick that one up since I go by lightmann when I'm geocaching also. L - for lightmann.
One more is a bucket of obsidian chunks we picked up along the road on Hwy 395 in E. OR. There are tons of it just lying along the road close to the Battle Mtn. area. So we got out and picked up a bucket full.
Rocks are cool.