Mining of the ruby mineralisation by Gemfields has been primarily focussed on three main clusters of production pits in separate areas, termed by Gemfields as Mugloto (the western portion of the deposit), Maninge Nice (the north-eastern portion of the deposit) and Glass (the south-eastern portion of the deposit).
The Montepuez ruby deposit is hosted by the Montepuez Complex, a strongly ductile-deformed, wedge-shaped, metamorphic terrane. The Montepuez Complex is composed of orthogneisses ranging from granitic to amphibolitic in composition, and para gneisses comprising quartzite, meta-arkose, marble lenses, quartz-feldspar gneiss, and biotite gneiss. These metamorphosed sedimentary rocks have been intruded by granite, granodiorite, and tonalite.
Intense deformation has resulted in a highly complex structural framework, with the local units folded into tight and isoclinal folds dissected by a suite of mainly northeast to southwest trending shear zones.
The Montepuez Complex is bounded by thrust faults to the north by the Nairoto Complex, the oldest rocks in the region composed of ductile-deformed metamorphosed intrusives, and to the west by volcano-sedimentary meta-suites of the Xixano Complex.
Ruby and corundum mineralisation is found in two styles: primary amphibolite, and a secondary gravel bed. The main source of rubies and corundum is secondary mineralisation, although mining has also occurred from the primary mineralisation. T ........
