Colour varieties of Afghan beryls from pegmatites at Ghursalak in Konar Province (aquamarine, morganite) and from the Panjshir Valley (emerald) have been investigated. The aquamarine, composition with SiO2 (65.75 wt.%), Al2O3 (17.87 wt.%) and BeO (12.29 wt.%) is similar to that of many other aquamarines, and the low concentration of alkalis as well as relatively high amounts of Li2O (0.34 wt.%) all indicate the gemstone to be normal beryl with limited isomorphous substitution in octahedral and tetrahedral sites. The calculated unit cell parameters (i.e. a = 9.2221 angstrom, c = 9.1990 angstrom, c/a = 0.9975), optical characteristics (i.e. omega = 1.576, epsilon = 1.571; Delta = 0.005) and the IR spectra of aquamarine with characteristic bands at 1206 and 963 cm(-1) are typical of normal beryl. Emerald with contents of SiO2 (64.50 wt.%), Al2O3 (15.19 wt.%) and BeO (12.73 wt.%) and significant amounts of alkalis (i.e. Na2O+K2O+Li2O = 2.1 wt.%) is alkali-rich octahedral beryl. This attribution is also indicated by the unit-cell parameters (i.e. a = 9.2399 angstrom, c = 9.1984 angstrom, c/a = 0.9955) and optical characterization (i.e. omega = 1.580, epsilon = 1.574; Delta = 0.006). Morganite with SiO2 (64.16 wt.%), Al2O3 (17.91 wt.%) and BeO (11.81 wt.%) has the highest total alkali content (Na2O+K2O+Li2O = 3.51 wt.%) and is assigned to alkali-rich (Na-K-Li) tetrahedral beryl. The IR spectra of morganite (additional band at c. 1060 cm(-1), no shifts of 1215, 970 cm-1 towards lower wave numbers) together with calculated unit-cell parameters (i.e. a = 9.2198 angstrom, c = 9.2314 angstrom, c/a = 1.0012) and optical characteristics (i. e. omega = 1.580, epsilon = 1.574; Delta = 0.006) are all typical for a tetrahedral beryl. The Afghan beryls formed within granitic, beryl-muscovite pegmatites in hydrothermal conditions.
