Some kind of Mica?
Looks kind of like slate (Mica in it), shale or mudstone. Biotite (A Mica), maybe?
Biotite:
http://mineral.galleries.com/minerals/silicate/biotite/biotite.htm
Slate:
http://seis.natsci.csulb.edu/bperry/metarock/SLATE.htm
Looks like there may be a strip of this stuff running up and down the picture. Of course, like many rocks on Mars, it could have originated somewhere else on the planet and been blasted to this spot by an impactor.