Media playback is unsupported on your device

What makes a really rare mineral?

Scientists have categorised the Earth's rarest minerals.

None of 2,500 species described is known from more than five locations, and for a few of them the total global supply could fit in a thimble.

The researchers say it is important to hunt down these oddities because they contain fundamental information about the construction of our planet.

Dr Robert Hazen, from the Carnegie Institution in Washington DC, spoke about the project to our correspondent Jonathan Amos.

  • 13 Feb 2016