Morphology and surface mapping

Of the many boulders photographed at the Apollo 17 site, boulder 1 from Station 2 is unique in having a strongly developed foliation. Resistant layers form four steeply inclined ridges separated by joint planes or by deeply eroded beds of softer materials. A prominent cleavage, or set of cross joints, is oriented almost normal to the foliation. The cleavage is expressed as subparallel cracks, some of which are open fissures. The entire surface of the boulder is rough and studded by dark colored knobs ranging in diameter from 1 to 15 cm. It is a polymict breccia containing at least one type of rock that has not been recognized in any other lunar sample, and it records an unusual minor element distribution and magnetic history.