We did the same thing a couple weeks ago near Hector Road and I 40. The rocky plain is called Desert Pavement. It's the washout from the surrounding hills and is the best place to find quartz, agate, jasmine, and other cool "polishing" size stones. We collected tons of them and are waiting for a geologist friend of ours to come back from vacation and set us up with polishing gear.
We also went spelunking in the lava tubes there. Then the wind kicked up to about 80 and we thanked God we had a motorhome.