GEOLOGY: The precambrian emerald deposits are in a ductile shear zone region, the Nugrus Thrust, which divides two domains, the Central and Southern Eastern Deserts.  The emerald schist zones along this thrust are the Zabara, Sikait, and Um Kabu.

The emeralds are commonly restricted to volcanosedimentary series. The whole sequence occurs as imbricated structures affected by complex folding and deformation. Folding has been intense and repeated, forming a series of ripples.

The rocks are mainly schists, serpentines and granites, together with various type of aplite, pegmatite, beryl and fluorite veins and dike rocks. The most abundant schists are mica and talc types but it is also present actinolite, chlorite, tourmaline, quartz-muscovite and graphite schist. All are cut by tourmaline veins. Basement rocks is made of metasediments and metavolcanics intruded by granites. Serpentines from the summit of Gebel sikait overlie the schist and intruding later. Granitic rocks are younger than schist and serpentines, they included foliated gneissose rock containing numerous subparallel pegmatitic muscovite veins and sometimes fluorite veins.  Also present is a white intrusive granite (derived by dehydration melting of metapelitic schist, which is believed to be younger than gneiss. Beryl occurs in biotite-quartz, and actinolite-biotite schist, and tourmaline-mica schist.