Q. What accounts for the color differences in diamonds?
A. In diamonds, unexpected colors may arise in a variety of ways. These include small and large inclusions of other elements in the crystal, physical deformation of the crystal lattice, radiation, or a combination of causes. All affect how a stone absorbs and reflects various wavelengths of light.
The jeweler’s familiar range of colorless to yellow or yellow-brown diamonds depends on distributions of nitrogen atoms, a connection that was not discovered until 1959.
The famous and rare blue diamonds, like the notorious Hope diamond, have varying quantities of boron atoms in their crystal lattices. But the intensity of color is only loosely correlated with the concentrations of boron.
The even rarer pink and red diamonds owe their color to subtle physical shifts in the alignment of the crystal planes that happen as they are subjected to extreme heat and pressure as they rise from the great depths of the Earth.
Radiation deforms some crystals, producing green diamonds. Purple diamonds result from both hydrogen inclusions and physical deformation.
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