Just plain-ole basalt. Dull, right? Well, yes, it can get tedious in a state so well endowed with that rock, but it can be interesting if there's something more than just plain-ole black ugly rock. In this case, the white splotches down lower are mostly Queen Anne's Lace. But the speckles up higher are calcite and zeolites, and those are pretty and interesting. The best way to look for them here is by splitting the cobbles and boulders that have fallen off the face and into the ditch/berm. The road is windy here, and traffic is sporadic, and often moving faster than is wise. Keep your ears pealed; you'll hear vehicles before you see them. There's plenty of off-pavement space, so give them some room.