Scientists studied the mineralogy and bulk rock composition of these unusual achondrites and found them to be almost identical to those of some Apollo moon rocks. They are also distinctly younger than other meteorites (less than 4 billion years) and similar in age to lunar highland rocks. There are also basaltic meteorites from the dark-colored lunar mare.
These similarities with Apollo moon rocks and differences from other achondrites make this group of lunar meteorites the only group of meteorites for which scientists are certain of their parent body. They were presumably blasted off the Moon by several meteorite impacts and eventually landed on Earth. There are 11 distinct meteorites (15 separate collected fragments) which are from sites in the highlands and mare regions of the Moon. Studies of these random lunar samples supplement the information obtained from the nine regions of the Moon sampled by the American Apollo and Russian Luna missions.
Reproduced from http://www-curator.jsc.nasa.gov/