The alluvial sapphire profiles of Mayo Kewol placer in the Adamawa region (North-Cameroon): Granulometric and mineralogical features

In the Adamawa mining region (Cameroon), a geological and mining survey of alluvial sapphires in the Mayo Kewol (Mayo means stream or river) area was carried out in order to characterise the sedimentological and mineralogical features of the placer. The studied profiles overlying the substratum were made up essentially of mineralized gravel, sand, clay and humic silt. Sapphire hosted in alluvium is associated with ruby, topaz, beryl, zircon, monazite, cassiterite, magnetite and ferrocolumbite. Sapphire grains were in the greater part subblunt and blunt shining, sometimes round and dull or were found in primary relictual morphology with encrusted quartz, monazite and ferrocolumbite on their surfaces. These results indicate the diversity of mineralized sources with both far and nearby origins.