THE DIAMOND PAGE — Trenching unearths diamondiferous gravels in central Africa

Trenching by partners United Reef (URP-T) and Trans Hex International (THXI-C) has uncovered diamond-bearing gravels along a bank of the Bangoran River in the Central African Republic.

The discovery was made 8 km from the Bamingui property, where the partners are currently producing diamonds from a 30-tonne-per-hour processing plant.

To date, the companies have completed bulk-sample trenches across the alluvial flats that mark the present drainage of the Bangoran River. The first trench, located at the headwaters of the river canyon, intersected a thin layer of poorly sorted gravels that were found to be weakly diamondiferous.

The second trench, excavated 500 metres down-river, returned an average grade of 6.03 carats per 100 tonnes, with an average diamond size of 0.42 carat per stone. The third trench, excavated a further 200 metres down-river, returned an average grade of 4.96 carats per 100 tonnes. Results from other trenches are pending, and the partners intend to test the extent of the diamond-bearing gravel horizon.

The partners report that individual 95-tonne bulk samples (from trenches 2 and 3) returned grades ranging from 2 carats per 100 tonnes to 9.19 carats per 100 tonnes, with individual diamonds ranging in size from 0.09 to 1.76 carats in weight. To date, bulk sampling at the Bangoran River has yielded 382 diamonds with a total weight of 103.3 carats, the average diamond size being 0.27 carat per stone.

United Reef expects the average value of diamonds from the river will be similar to that of gems extracted from the Bamingui River mine. That deposit has produced diamonds with an average sale value of US$188 per carat.

To date, just over 4,800 carats have been produced from the Bamingui River, resulting in proceeds of $1.2 million. United Reef holds an 80% interest in the project, with local interests holding the remainder. The project is being developed through a joint venture held 68% by United Reef and 32% by Trans Hex.

A gold circuit was recently added to the diamond recovery plant at Bamingui River and, based on metallurgical testwork, United Reef reports “excellent” gold recovery through gravity separation.

Gold concentrate samples were obtained from the Bangoran River and sent for additional testwork to determine the amount of gold contained in the gravels.

Results are expected in October.