The Aurora Pyramid of Hope
Alan Bronstein and Harry Rodman · Collection assembled from 1980 onwards; on loan since 2005
At the far end of the Minerals gallery, behind a heavy door, the Vault holds the museum's most precious stones, and none draws more gasps than the Aurora Pyramid of Hope. Nearly three hundred diamonds are arranged in a rising triangle, and not one of them is white. They run through every colour a diamond can be: canary yellow, cognac brown, olive green, steel grey, lilac, pink, orange, blue and the almost black stones at the base. Together they weigh about two hundred and sixty seven carats and form the most complete collection of naturally coloured diamonds in the world.
Colour in a diamond comes from tiny imperfections. Nitrogen atoms trapped in the crystal lattice give yellow and orange; boron gives blue; distortions of the lattice under pressure deep in the Earth give pink and red; exposure to natural radiation over millions of years gives green. Press the button beside the case and the lights change to ultraviolet, and the pyramid glows in an entirely different set of colours as the stones fluoresce. That is the moment most visitors remember. Each diamond is cut in a different style, so you can compare the way a brilliant cut, a pear and an emerald cut handle light.
The collection was assembled over twenty five years by the New York gem dealers Alan Bronstein and Harry Rodman, who bought coloured diamonds at a time when the trade regarded most of them as flawed. It was shown at the Smithsonian and then lent to this museum in 2005. The Vault also holds the Latrobe gold nugget, a piece of the Nakhla meteorite from Mars and the Devonshire emerald.
Did You Know? Under ultraviolet light some of the diamonds switch colour completely, so a yellow stone can glow blue.
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