77515 is an impact melt breccia apparently similar to 77135. The texture of 77515 is poikiloblastic with irregular pigenoite oikocrysts enclosing abundant euhedral plagioclase laths and tablets and minor rounded olivine grains. Ilmenite is dispersed throughout and is also poikilitic. The mineral mode consists of 52.7% plagioclase, 44.5% pyroxene and 2% ilmenite. Lithic clasts include devitrified anorthosite and earlier-formed breccia clasts, although these do not appear in our thin section. The rotations show two different types of plagioclase feldspar - shocked (rotation 1) and unshocked (rotation 2). Metallic iron mantled by troilite is visible in reflected light.
The sample weighed 337.6 grams before analysis and has not been dated.
Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/
Apollo 17, the final manned landing mission, had two objectives: to obtain samples of ancient rocks from the lunar highlands and to look for evidence of younger volcanic activity on the valley floor.
This small Collection contains material deriving from both periods, including igneous rocks around 4.3 billion years old from the lunar highlands as well as younger volcanic samples dating from about 3.6 billion years ago.
Apollo 17 was launched on 7 December 1972.