You might have heard the term 'designer drugs', but 'designer chemicals' are also a big business. Californium 252 is a special isotope that's used to find the layers of water and oil in oil wells. This synthetic radioactive element has a half-life of 2.645 years and is produced by nuclear reactors.

The chemical was first made in 1950 at Berkeley in California and can cost a jaw-dropping $27.8 million (£20.6m) per gram, or $765 million (£567m) per ounce.