corundum, violet sapphire, Umba Valley, Tanzania.12, East Africa, gems

Bank, Berdesinski and Ottemann describe violet gem-quality corundum from the Umba region of Tanzania. The brief paper examines the mineralogical and gemological properties of the violet material and its relationship to other fancy-colored corundums from this important East African deposit. Particular attention is given to the coloration of the stones and the trace elements responsible for it, together with physical and optical properties useful in characterizing the material. The occurrence adds violet corundum to the wide range of ruby, sapphire, and fancy-colored corundum known from the Umba area.