15386 is the largest sample of pristine KREEP basalt in the Apollo collection. By pristine we mean that it is lacking in meteoritical siderophiles (Ir, Re, Au etc), and hence not contaminated by meteorite debris. Thus it is thought to represent an indigenous lunar volcanic melt derived from the lunar interior. Plagioclase laths are surrounded by interstitial pyroxene. The cores of pyroxene crystals are Mg-rich orthopyroxene. They are surrounded (overgrown) by pigeonite with patches or rims of subcalcic augite.The mesostasis has significant cristobalite (10%), ilmenite plates (3%), and minor phosphate, metallic iron and troilite. Rotation 2 shows one of the interstital melt pockets enriched in these minerals.
The sample weighed 7.5 grams before analysis and has been dated at 3.85±0.08 billion years (Sm/Nd).
Our sample has been used for laser-ablation analysis and displays many circular black pits where material has been removed. It has also been gold coated for SEM analysis and although most gold has been cleaned off, some remains in fractures.
Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/
KREEP is an acronym built from the letters K (the atomic symbol for potassium), REE (Rare Earth Elements) and P (for phosphorus). It is a geochemical component of some lunar impact breccia and basaltic rocks.
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.