MINING IN AFRICA SPECIAL — Tan Range plans bulk sampling

As soon as the dry season arrives in April, Vancouver-based Tan Range Exploration (ASE) plans to begin bulk sampling at its Tabora diamond concession in central Tanzania.

The property comprises 20 sq. km. and hosts several known kimberlite bodies, including a Z-shaped kimberlite fissure with a strike length of 750 metres measuring 2.9 hectares in size. This fissure, or dyke, outcrops on surface and contains kimberlite breccia facies in the centre. The body is not a new discovery, and was bulk-sampled in the past by De Beers. This work is reported to have returned diamond values as high as 57 carats per 100 tonnes, with the largest stone recovered weighing 7.11 carats. Tan Range reports that another similar kimberlite body was discovered 400 metres north of the Z-shaped fissure already described. The company says test pitting and drilling will be required to determine if this new discovery, located on trend, is connected to the fissure.

Some diamond indicator mineral geochemistry has been conducted on the concession by Scientific Services of South Africa, which estimates a grade of 40 carats per 100 tonnes. (This estimate is in line with bulk-sample results obtained by De Beers.)

Tan Range intends to use a 25-cubic-metre-per-day rotary pan for the bulk sampling. The first stage will involve processing 250 cubic metres. If results are favorable, a further 250 cubic metres of material will be processed.

Tan Range has two other diamond properties in Tanzania, N’Gwamanonga and Nyangwahale. The company is awaiting government approval of concession applications covering an additional 17,000 sq. km.

Tan Range’s Tanzanian subsidiaries also have accumulated gold properties in the country. These were acquired for their potential to host large-tonnage, open-pit, heap-leachable reserves similar to those being developed in Western Australia.