Tongo Diamond Fields are the richest diamond resourcess in Sierra Leone - 18,897,150 carats worth US$3.3 billion.
Independent Consultant Values Tongo Fields at US$3.3 Billion; 18.9 million carats at US$175/carat.
In 1996 geologist Dr. Luc Rombouts has prepared a report on the Tongo Fields fissures. Dr. Rombout's review was based upon bulk sampling and drilling carried out in the past by Sierra Leone Selection Trust (SLST), which work was summarized in a study carried out by Seltrust Engineering in the 1970's. Dr.
Rombout's report states that the Seltrust Engineering study can be used as a basis for a provisional resources estimate.
There are four known dyke zones in the Tongo Fields.
The richest grades were encountered in the Lando dyke zone. SLST bulk sampled the Lando dyke zone at 122 meter intervals and at a depth down to 10.36 meters, yielding 9,466 carats out of 1,349 cubic meters, being a grade of 2.69 carats per tonne.
Drilling was carried out over a strike length of 2,600 meters. Seltrust Engineering concluded that the Lando dyke zone contained 1.68 million carats down to a 300 meter depth at an average mining grade of 0.80 carats per tonne. Sierra Leone's alluvial diamonds are currently averaging US$200 to $300 per carat.
Assuming an average value of US$175 per carat for the Tongo diamonds, the material should have an average value of US$140 per tonne, including mining dilution over a stope width of 1 meter.
In his report, Dr. Rombouts calculated the potential diamond content of the Lando dyke zone as well as the other three dyke zones, by extrapolating the grade and width over the total potential length of the four dykes to a depth of 1,000 meters.
These calculations are based upon assumptions concerning depth and continuity of grade, and are subject to confirmation by the bulk sampling and drilling to be carried out.
The Tongo kimberlite dykes have been sampled, drilled and worked at the surface in the past. Workings never extended deeper than 15 m.
The TONGO dykes are very rich (up to 3 carats/tonne) and constitute an important high quality diamond resource. The continuity of the dykes with depth has been proven down to 100 m by drilling by SELECTION TRUST.
Over a total strike length of 14,400 m and a depth of 1,000 m the TONGO dyke system constitutes a huge diamond resource of 18,897,150 carats worth US$3.3 billion.
Small pipes are known along the LANDO dyke zone and could further increase the resource figure. Assuming a value of at least US$175/carat for the diamonds in the LANDO kimberlites and allowing for a mining dilution over a 1 m stoping width, the average value content is US$140/tonne, amongst the highest in the world.
Total operating cost should remain well below US$50/tonne
Tongo Fields alone represents a potential gross profit of at least US$1.4 billion for DMW.
Regards TA
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