These are two fragments of Apollo
16 sample 60025, a pristine cataclastic anorthosite. This samples
consists almost entirely of plagioclase feldspar. The term cataclastic
implies that it is shocked and fractured by meteorite impacts, which causes
the opaque white color as opposed to the translucence one sees in
terrestrial plagioclase-rich rocks of this size. A millimeter scale is just
visible in the lower left corner. Click on image for enlargement.