desert varnish. It is now known that up to 70% of the coating is composed of clay size particles that act to trap iron and manganese oxide grains that arrive on the wind.
A nice dinner circle was made while overnighting at Rattlesnake camp. I would say that this is one of my favorite times of the day, when our day hikes and river running is complete and we can relax and enjoy the clean air, some conversation and the company of like-minded friends. I often will help folks to 'fill in the blanks' on their river guidebooks in settings such as this.