THE KYANITE DEPOSITS OF CHEMBI, ETHIOPIA

2. Graz University of Technology, Inst. of Eng. Geology and Applied Mineralogy, Austria

ABSTRACT

The Chembi Kyanite deposit is hosted by a thin belt (100 – 300m in width) of kyanite-quartz schist which extends continuously for more than 30 km. Kaolinized kyanite-quartz-mica schists occur intercalated with the kyanite-quartz schists. Its mode of occurrence suggests a product of regional metamorphism of pelitic sediments (probably shales and clay-muds) under high-pressure conditions.

Mineralogical analyses of samples collected from trenches indicate average bulk mineralogy of 27% kyanite, 68% quartz and 5% other minerals (mica, rutile, and kaolinite). On the basis of optical studies performed to determine the degree of liberation nearly all the materials below 630 ?m size fractions are free from interlocked grains.

Concentrated kyanite samples have Al203 content in the range of 54.8% to 61.2%, averaging 57.6%. Total iron and alkali contents are 0.2% and less than 0.1%, respectively. All the impurity elements are below the maximum acceptable limit for commercial grade kyanites.

Preliminary trials to concentrate the kyanite by flotation shows a grade of 97% and 96% kyanite and quartz respectively with a recoverable weight percent of about 25% kyanite and 60% quartz. This deposit with its high quality kyanite free from any iron contaminant is comparable to most of the kyanite deposits of the world which dominate the current kyanite markets.

Based on detail mapping on a selected area and reasonable geologic inferences the kyanite ore in the entire region is estimated to be over ten million tons.

Note: This work was done as a continuation of the LRG Project "Utilization of
Refractory Raw Materials in Ethiopia" which had been carried out by the author and the co-researcher. The study was done at the Graz University of Technology, Austria. The report is available at the Central Technical Library of the ESTC.

(Final Report 1995)

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