Xenomorphic Olivine Inclusion in Diamond
The author recently examined a faceted diamond that contained an oddly shaped near-colorless crystal with a low-relief tension crack surrounding it. The inclusion was identified by Raman spectroscopy as olivine, a rather common inclusion in diamond. The remarkable thing about this particular example was its shape, which consisted of three spokes intersecting at approximately 120° (see above). This is not the shape one would typically associate with the orthorhombic mineral olivine, but there is an explanation for the unusual morphology of this inclusion.
As diamonds form at extreme temperature and pressure conditions, they can impose their morphology on syngenetic minerals that become included in them. When a guest mineral adopts the host diamond’s morphology, this is known as xenomorphism. The triangular morphology seen here suggests that the olivine inclusion is oriented parallel to an octahedral crystal face of the host diamond crystal. This is one of the most unusually shaped inclusions observed in diamond examined by the author.
