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

Dislocation Chain in Oregon Sunstone

Jessa Rizzo

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.

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