To the left you see a logarithmic graph comparing the physical
abundances, by weight in the earth’s crust, of what many would
recognize to be the six most precious or “noble” metals. Ir, Au,
Rh, Pd, Pt, and Ag stand for iridium, gold, rhodium, palladium,
platinum, and silver respectively. These figures are at best
educated guesses, but according to most sources iridium is the
clear winner. It occurs at about four-tenths of a part per
billion, a ratio similar to that of a grain of salt to a
Clydesdale, making it about half again as rare as gold. The
silver shouldn’t surprise anybody, but look at all that platinum
we’re wallowing in. It’s a dozen or more times as abundant as
gold, though that’s largely offset by its greater difficulty and
expense of extraction. Its supply is also pretty dicey, as 80%
of it comes from South Africa. Before going further, we should
probably qualify our rare metal quest with “non-radiological.”
The Periodic chart arranges elements in rows and columns
according to their chemical pro