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

Emerald in Rock Crystal Quartz

Prismatic emerald crystal in quartz.
A prismatic emerald crystal within a rock crystal quartz. Photomicrograph by Nattida Ng-Pooresatien; field of view 12.5 mm.

Rock crystal is a transparent and colorless macrocrystalline variety of quartz (SiO2) that often has cavities containing liquid and gas two-phase inclusions. Many different minerals also form as inclusions within rock crystal quartz. Typical varieties of included quartz for gem use are rutilated quartz, tourmalinated quartz, and strawberry quartz. Specimens may also contain several other types of mineral inclusions.

Recently, the author examined a 10.95 ct rock crystal quartz cabochon that contained elongate rod-shaped green crystals (see above). The green crystals showed hexagonal cross-section and were identified by Raman spectroscopy as beryl. Ultraviolet/visible/near-infrared (UV-Vis-NIR) spectroscopy showed a chromium (Cr) spectrum, which confirmed that the green crystals were emerald. This amazing inclusion has been previously reported in a rock crystal quartz specimen (Fall 2008 Lab Notes, p. 258), but this is the first time the author has examined a gem-quality rock crystal quartz cabochon with a perfectly hexagonal emerald crystal inclusion.

Nattida Ng-Pooresatien is senior staff gemologist at GIA in Bangkok.