Micro-World Gems & Gemology, Fall 2019, Vol. 55, No. 3

Dislocation Chain in Oregon Sunstone

Rectangular dislocation chain in an orangy red Oregon sunstone.
This orangy red Oregon sunstone contained an interesting decorated dislocation that was visible using fiber-optic illumination. Photomicrograph by Jessa Rizzo; field of view 4.79 mm.

The author recently examined a high-quality faceted orangy red Oregon sunstone weighing 6.77 ct. Examined under magnification with fiber-optic illumination, the stone displayed an unusual inclusion that consisted of a decorated dislocation string (see above). Copper exsolution platelets, which are common in Oregon sunstone, were also observed. In this example, the decorated dislocation followed a rectangular pattern, consistent with the crystal structure of the host feldspar. This unique light-scattering dislocation chain is the first that the author has encountered in Oregon sunstone.

Jessa Rizzo is a staff gemologist at GIA in Carlsbad, California.