Lab Notes Gems & Gemology, Winter 2016, Vol. 52, No. 4

Dyed Green Beryl

A green dye concentration observed in beryl.
Figure 1. A green dye concentration in beryl was observed along fractures and confirmed by spectroscopic testing. Photo by HyeJin Jang-Green.

Emerald simulants and synthetic emeralds have often been submitted for testing to GIA (e.g., Spring 2001 Lab Notes, pp. 57–59). Recently, the New York laboratory examined a dyed green beryl that was intended to imitate natural emerald. The green octagonal step-cut stone, set in a yellow metal ring with near-colorless stones, initially appeared to be emerald.

The stone had a refractive index of 1.588–1.595 and fluoresced a very weak chalky yellow under long-wave UV radiation and a weak chalky yellow under short-wave UV. Microscopic examination revealed the obvious presence of a green dye concentration in numerous fractures (figure 1) and other natural beryl inclusions such as short needles, particles, and jagged fingerprint patterns. This dyed green material also enhanced the clarity of the stone.

In addition, dyed bands (~610 and 660 nm) were revealed in the visible spectrum by utilizing a high-resolution visible spectrometer (figure 2). The green color in this sample was caused by an organic dye rather than chromium or vanadium elements that give rise to a green color in natural emeralds. When the color was observed under a diffused light source, it became apparent that a near-colorless natural beryl was the starting material. This example shows the importance of spectroscopic testing to confirm the cause of an emerald’s color.

Vis-NIR absorption spectra.
Figure 2. In the beryl’s Vis-NIR absorption spectrum, dye bands were observed at ~610 and 660 nm, while sharp Cr-related features were absent.

HyeJin Jang-Green is a staff gemologist at GIA in New York.