L5

regolith, but "The High Frontier" suggests that by weigth, it is
typically 40% oxygen, 20% Silicon, and 20- 30% metals (aluminum, iron,
magnesium, titanium). Is there a more up-to-date assay?

> Now, about the overall content of the moon.
>
> Free metal concentrations in stony meteorites are about 20%, compared
> to a few hundred ppm in the lunar regolith. The only way that I see he could get to "ppm" is by using "free metal" to mean metal unbound to oxygen atoms. But of course that's what ore refineries are for. The figures you've been seeing are correct for iron in the form of iron oxide, aluminum in the form of alumina oxide, etc.
Regards,
Mike Combs