Omphacite in Pink Diamond
Photomicrography of colored crystal inclusions is a field of seemingly endless possibilities in the realm of colored stones. With regard to diamond, however, the possibilities are far more limited. This is due to the growth origin of diamond within the earth’s mantle—an environment few other minerals are able to endure. While colored crystal inclusions in diamond are uncommon, known possibilities include garnet, diopside, corundum, olivine, kyanite, and omphacite, the latter of which was seen in the Fancy brown-pink diamond in the above figure and identified via Raman spectroscopy.
Omphacite is a mineral within the clinopyroxene solid solution series, which also contains the members jadeite, diopside, and aegirine. It typically occurs in eclogite, a high-pressure, high-temperature metamorphic rock also containing garnet. Eclogites form from igneous oceanic crust that has subducted into the mantle. The presence of an omphacite inclusion proves the diamond formed in an eclogitic environment. This is a rare inclusion not often seen at GIA.
