While I was at Playa I would constantly stoop down to pick up pebbles from the gravel drive. Although the drive looks gray at first glance the individual rocks were of extraordinary variety. I gradually laid them out on the boardwalk in front of my cabin (ala Andrew Goldsworthy - although my little pet rock project is not worthy of that association). I'll also post it on my Flickr page so you can view it larger and scroll back and forth.
-hmmm. That didn't work either. I'll figure it out later.