Zambia is considered the world’s second most important source of emeralds by value (after Colombia). The deposits are located near the Kafubu River in the Ndola Rural Restricted Area. Emeralds have been known from this region since 1928, but significant commercial production began only in the 1970s. As of mid-2004, most of the emeralds were being mined from large open-pit operations at the Kagem, Grizzly, and Chantete concessions. Economic emerald mineralization is confined almost entirely to phlogopite reaction zones adjacent to Be-bearing quartz-tourmaline veins that metasomatically altered Cr-bearing metabasite host rocks. Nearly all of the rough is cut in India and Israel. Zambian emeralds have relatively high R.I. and S.G. values, with inclusions typically consisting of partially healed fissures, as well as actinolite, phlogopite, dravite, fluorapatite, magnetite, and hematite. They contain moderate amounts of Cr, Mg, and Na, moderate-to-high Fe contents, and relatively high Cs and Li. Although many features of Zambian emeralds are comparable to those from other commercially important localities, in many cases they may be separated by a combination of their physical properties, microscopic characteristics, and chemical composition.
Table 1: Local Geological Terminology for the Kafubu Emerald Area
Table 2: Chemical Composition of Zambian Emeralds by Electron Microprobe
Figure: Fluid Inclusions in Zambian Emerald Containing CO2 and CH4
Submitted by Brendan M. Laurs
August 18, 2005