Block Island - Sol 1961 (False Colors; credits: NASA/JPL-Caltech/Cornell University)

Caption NASA:"This view of a rock called "Block Island", such as the largest meteorite yet found on Mars, comes from the Panoramic Camera (PanCam) on NASA's MER (Mars Exploration Rover) Opportunity.
Analysis of Block Island's composition using the Rover's Alpha Particle X-Ray Spectrometer confirmed that it is rich in Iron and Nickel. The rock is about 60 centimeters (approx. 2 feet) across.

This is a False-Color, red-green-blue composite view generated from images taken through the PanCam's 750-nanometer, 530-nanometer and 430-nanometer filters. The exaggeraged color is used for enhancing the visibility of differences among the types of rock and soil materials".