Troctolite 76535

It was collected by geologist astronaut Harrison Schmitt as part of a "rake sample" of lunar soil at Geology Station 6, near the base of the North Massif.

[2] Olivine and plagioclase are of about equal quantities within 76535, while the remaining approximately 4% is made up of primarily orthopyroxene.

According to early studies, the sample cooled at a depth of about 10–20 kilometers (6.2–12.4 mi), as well as its reequilibration and annealing.

[3] Later work indicated that the rock formed at a depth of 47 kilometers,[4] about the middle to lower crust of the Moon,[5] Investigations have shown that the rock may have formed as a cumulate at depth, thus possibly making the sample an important link in the understanding of the geologic timeline of the Moon.

[6] As Troctolite 76535 is the oldest known "unshocked" (meaning unaltered by meteor impacts) lunar rock, it has been used for thermochronological calculations in order to determine whether the Moon formed a metallic core or generated a core dynamo.