GEOLOGY

More resistant emerald crystals might be found in the alluvial placers along the flat shores of Lake Maniara. 

The geology of the Maniara lake beds, which are of Pleistocene age:  The faulting system of the Rift Valley is of highest importance. The Gregory Rift Valley is formed by a westerly-tilted block bounded on the West by the Maniara fault scarp, and on the East by a series of small normal faults thrown down to the East just outside the eastern margin of the sheet.

The irregular NNE line of the Manyara Escarpment results from a combination of arcuate faults swinging between NE and NNW with a series of NE strike faults. Minor blocking-faulting is produced by a combination in the Hassam area. The strike faults have engendered vertical and horizontal displacement of the bands, and the veins traversing small joints intersecting the biotite rocks which normally strike W 260°-270° in all direction, but predominantly in NW-320° trend.

The most ubiquitous rocks round the area are the mica schist, amphibolites with bands of mica, chlorite schist, amphibolite gneisses, kyanite, almandine, amphibolite gneisses and the highly granitoid gneisses. Two types of gneisses are distinctive in this region. The banded gneisses are of quartz-feldspatic metasedimentary rocks.