Why process one million tonnes of rock to make just 3.8 kilos of iridium?

Professor Martyn Poliakoff, host of the excellent series Periodic Table of Videos, is still in the Johnson Matthey labs and this time showing off a 3.8 kilogram iridium bar.

"Iridium is the densest metal that exists. It has one of the highest melting points, as well," says Poliakoff, who is also a chemist at the University of Nottingham.

"To get this bar one has to process about 600,000-700,000 tonnes of rock—a huge amount of rock, nearly one million tonnes of rock just to make this."

That high melting point makes the metal important in a wide variety of industrial uses, such as making spark plug tips where other metals would just corrode out due to the high temperatures.

"It's important to stress that modern technology depends on making these tiny, tiny components of iridium and getting them in the right place."

In May Poliakoff was in the Johnson Matthey lab looking at platinum.

Earlier this year he mourned all gold locked away in the Bank of England.