re: Rolling boulders.
For some reason [hey, Robert!], the IMG tag you posted was truncated to oblivion - I searched through the MGS captioned released for 1998 and found what I think you meant:
this?
Kinda hard to tell from that pic that the cracks are truly radial - whether or not they are, by the time they reach the crater's rim they'd look parallel anyway. But I get, now, that they can't be rolling boulder tracks.
The layered igneous/metamorphic rock I saw (and climbed over) was at the southeastern tip of Vancouver Island, BC. There were thin quartz layers running through the granite, too.