Hafnium is one of the more obscure members of the periodic table. It is familiar to engineers in nuclear reactors who make extensive use of it in the form of control rods: big bars of this metal that are inserted into a nuclear reactor chamber as brakes to avoid overheating. Given its superior resistance to chemical attack and oxidation, as well as its extremely high melting point, it’s little wonder that it also plays a prominent role in the making of rocket and turbine engines where these properties are critical.

Fewer than 100 tons of hafnium are recovered each year and the price has multiplied in the past few years.