Archaeological geology of Wadi Sikait

Abstract

Emerald, a green transparent variety of beryl, was one of the most highly prized gemstones in antiquity. The earliest known emerald mine is located in the valley of Wadi Sikait in Egypt’s southern Eastern Desert, where mining probably began toward the end of the Ptolemaic period in the 1^st century BC. Most of the mining activity, however, dates to the Early and Late Roman periods (1^st to mid–2^nd centuries and 4^th to early 6^th centuries AD, respectively) with much reduced activity during the Middle Roman period (late 2^nd to 3^rd centuries AD). The Romans referred to emerald as smaragdus and named the Sikait region Mons Smaragdus or Emerald Mountain. An archaeological geology survey of Wadi Sikait was undertaken for the purpose of mapping the distribution of ancient mine workings, deducing the ancient mining methods, and describing the geologic occurrence of emerald. It was found that emerald and other green beryls occur within the contact zone between phlogopite schist and intrusive quartz and pegmatite veins. The workings, which were excavated in the softer phlogopite schist with flat–edged chisels and pointed picks, are mostly shallow open–cut trenches that follow the quartz/pegmatite veins. Some workings continue as much as 100 meter underground and are still largely unexplored. Steatite and quartz mica schist also occur in Wadi Sikait and were quarried by the Romans for building stone.