77518 and 77519 were collected along with 77515 and 77511 soil. 77518 is similar to 77549, but finer grained. The texture is microgranular-micropoikilitic with numerous xenoliths of calcic plagioclase. A portion of the sample has K-rich, silca-rich glass for matrix. One large olivine clast contains symplectite. A pink spinel with a dark reaction halo is shown in rotation 1. Unusual lamellar twinning in a rounded clast of plagioclase feldspar is shown in rotation 2. Metallic iron mantled by troilite is visible in reflected light.
The sample weighed 42.5 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.