Something New on Mars...

Interesting image in today's raw image dump from Curiosity (on Mars).  This one is from the MHLI camera, showing a close-up of the rocky surface.  You can see the little “blueberries” frequently observed on the Martian surface, but there's also something new (to me, at least): the white bits that look almost like someone filled in some pits with silicone rubber caulking.  Other images in the same series show even more of this.  There's no explanation posted for this yet, so I have no idea what that white stuff actually is (I'm certain it's not really silicone rubber caulking :)