TABLE 1. Physical properties of emeralds from Fazenda Bonfim, Rio Grande do Norte, Brazil.
Color Very light to medium-dark slightly bluish green to strongly bluish green; typically a saturated bluish green with a
light-medium to medium tone
Clarity Very slightly to heavily included
Refractive indices no = 1.587–1.591; ne = 1.578–1.583
Birefringence 0.008–0.009
Specific gravity 2.72–2.74
Pleochroism Distinct to strong; (light) yellowish green (o-ray), and bluish green to greenish blue (e-ray)
Fluorescence Inert to long- and short-wave UV radiation
Chelsea filter Pink to red (stones with saturated colors) or no reaction
Visible spectrum Distinct lines at ~636, 662, and 683 nm; partial absorption between 580 and 630 nm; and complete absorption