Hydrogen-rich diamonds: rare crystals with star-like zoning
Diamonds with a high concentration of hydrogen are named ‘hydrogen-rich diamonds’. These diamonds, with their unusual physical properties, are occasionally highly zoned, as is the case with the crystal shown here.
Typically, they are mixed and concomitant growths with grey-brown lobed cuboid sectors (rich in hydrogen) and octahedral sectors that are almost colourless (poor in hydrogen but rich in nitrogen aggregates).
The hydrogen-rich sectors (cuboid growth) are often also rich in aggregated nitrogen, as the latter is necessary for the integration of hydrogen, but the formation of N3 centres will be inhibited in these sectors when the hydrogen concentration is sufficiently high.
During growth, above a certain hydrogen content in the environment, hydrogen is integrated into several sites in the cuboid domains, but not (or only in very low concentrations) in the octahedral domains.
This type of diamond was described as ‘asteriated’ by René-Just Haüy (1743-1822) and Alfred Descloizeaux (1817-1897) because of the star shape formed by the lobes (sometimes called petals) when the stone is viewed from any face of the octahedron.
Such diamonds, like the 'Révélation' shown here, are very rare.
- Picture: Axel Respinger
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