Khenj is the main of Panjshir, it was formed where dolomite marbles and phyllites are crumpled into complex fold and are cut by concordant dikes of Permian-Carboniferous amphibolized gabbro-diorites, which are 60 to 100 m long and 2 to 3 m thick. Emerald
mineralization is localized predominantly in these dikes. The emerald
formed in small cavities at veinlet intersections in association with ankerite, dolomite, albite, quartz and pyrite. Accessory minerals are tourmaline (schorl and dravite), fuchsite, phlogopite, barite, rutile and parisite. The emerald
crystals are rather small, 5 to 15 mm long and 2 to 7 mm thick. Their colour is deep green.
Ref: E.Ya. Kievlenko (2003) Geology of gems, p. 96