Seams of shiny stuff
I normally carry a small iron-nickel meteorite in my pocket to fidget with. My meteorite is mostly covered with a black fusion crust. However the corners of the meteorite have been worn down to shiny metal by rubbing against the pocket's cloth. This martian iron-nickel meteorite has probably had parts of its fusion crust sand blasted away by long exposure to the Martian regolith. It's surface appearance is similar to my fidget rock.
The MER dataset is nicely accessible.
Gary