77516 is an olivine-microporphyritic ilmenite basalt similar to 71588. Large ilmenite blades penetrate sheaves of alternating pyroxene-plagioclase intergrowths. Phenocrystic olivine is overgrown (replaced?) with pyroxene (rotation 1). Pyroxene is sector zoned and also zoned to high iron enrichment (towards pyroxferroite compositions). Armalcolite, troilite, metallic iron and free silica are also present.
The sample weighed 103.7 grams before analysis and and has not been successfully dated. Generally Apollo 17 basalts are thought to be 3.73 billion years old.
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.