Aldrin was inspired by geology, because it “opened my eyes to the immensity of time.” Collins was not: “I hate geology — maybe that’s why they won’t let me get out on the Moon.”
Armstrong, displaying an impishness worthy of Pete Conrad, later admitted that he had been “very tempted to sneak a piece of limestone up” and place it into a rock box as a sample, to see what the scientists would make of it.
– David Michael Harland, The First Men on the Moon.
Apollo astronauts made visits throughout the 1960s to geology hot spots like Hawaii (“Incomparable display of recent basaltic volcanic features”), Oregon (“extreme range of differentiated volcanic rocks, obsidian flows, pumice cones, cinder cones and tuff rings,” and Iceland (“Probably the most moon-like of the field areas”).
Aldrin put his geology into practice when they reached the surface of the moon. From NASA’s wonderful transcripts:
109:49:40 Aldrin: Hey, Neil, didn’t I say we might see some purple rocks?
109:49:42 Armstrong: Find a purple rock?
109:49:44 Aldrin: Yep. (Pause) Very small, sparkly (garbled) fragments (garbled) in places (garbled) would make a first guess at some sort of biotite. (Pause) We’ll leave that to further analysis.
Aldrin got ribbed about this later, in that joshing-of-the-flyboys way, after the rocks turned out not to be purple (or biotite). Tough audience.
Another shot from the 1969 Texas trip: