London’s Natural History Museum is currently showing some of nature’s rarest treasures, including gems, crystals, and metals. Amongst them is ‘The Aurora Collection’, two hundred and ninety-six naturally coloured diamonds.
Only one in every ten thousand gem-quality diamonds is coloured. The colour comes from tiny impurities in the stone’s carbon lattice, or from minute defects in its structure.
“Each coloured diamond tells its own story, giving us insight not only into its formation but also to the deep Earth processes that took place when the gem was formed,” says Alan Hart, minerals expert at the Museum.
“For example, yellow diamonds are due to the presence of nitrogen in the structure, and green diamonds owe their colour to natural radiation damage. It’s an amazing opportunity to be able to display this unique collection of exceptionally rare gems at the Museum.”
Due to their scarcity, coloured diamonds can be worth astronomical amounts. Five or six figure prices are not unusual. Red stones tend to be the most expensive. There are less than twenty certified red diamonds in existence, and some of these have fetched over a million dollars per carat.