Aged, hard cheese
/The original paper (a copy, or a PubMed link if you really want it) includes measurements for a variety of Earth-bound minerals, moon rock samples, and seven cheeses, including the Swiss sapsago (a hard cow's milk cheese which is, due to added herbs, a bit green).
There's a lesson here: don't expect the newest hypothesis to explain everything, but don't blindly trust the old hypothesis, either.