15455 is an impact melt rock with significant clasts of plutonic rock. A large norite clast (not seen in our thin section) is one of the oldest lunar materials yet identified (~4.5 billion years). The matrix is described as a fragment-laden melt that has surrounded and intruded the enclosed clasts. The dark breccia matrix that makes up the majority of 15455 is coherent and dense in places and vesicular in others. It is composed of a seriate mix of plagioclase, olivine and minor pink spinel fragments (xenoliths) surrounded by a very fine-grained igneous-textured groundmass. Pyroxene is rare in the matrix material. Rotation 2 shows a small norite clast and rotation 1 shows two plagioclase-rich clasts (one altered to maskelinite).
The sample weighed 973.7 grams before analysis and has been dated at 3.94±0.04 billion years.
Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/
The Apollo 15 landing site was in the Apennine Highlands, and close to Hadley Rille — a long, narrow winding valley. Approximately 76 kg of lunar material, including soil, rock, core-tube and deep-core samples, were returned to Earth.
This mission was the first flight of the Lunar Roving Vehicle which allowed the astronauts to venture further from the Lunar Module than in previous missions. During three periods of extravehicular activity, or EVA, on July 31st, and August 1st and 2nd, Scott and Irwin completed a record 18 hours, 37 minutes of exploration, travelling 17.5 miles, in the first car that humans had ever driven on the Moon.
Apollo 15 was launched on 26 July 1971.