Unusual Dumbbell-Like Inclusion in Diamond
DiamondView luminescence images demonstrated that the inclusion was crystallographically oriented, parallel to the edge between two octahedral faces (figure 6). Dumbbell inclusions in HPHT synthetics have a clear crystallographic orientation, often along an octahedral edge as well.
But the stone fluoresced weak blue under long-wave UV radiation and was inert in shortwave UV, a classic luminescence behavior for natural diamond and unknown in synthetic specimens. Furthermore, the infrared absorption spectrum was typical of a natural type IaAB diamond with minor hydrogen. This proved the natural origin of both the stone and its inclusion. With magnification, the inclusion appeared colorless and transparent rather than metallic and opaque, though with a high optical relief. Its morphology was not cuboctahedral—as with inclusions in synthetic diamond—but rounded octahedral. The exact nature of the crystal remains unknown, as we could not obtain a Raman spectrum due to its intense luminescence, but colorless inclusions in diamonds are often forsterite.