I'm no expert on rocks but I have laid miles of spray paint down locating underground cables for 25 years. It sure looks like spray to me with the rough spots peaking through and the pooling in the valleys. See if it scratches off easily.
They got a good score today without me but my legs and lungs are getting a lot stronger. Soon I'll be able to go with Tom and pick up what he misses. I'll be at the outing to do some beeping and eating. I miss getting out a lot and it's sure better than that dang hospital. That wash has produced a lot of gold for us in the past and I am anxious to get in there and dig a little. Glad to see that it is still producing.