Saskatchewan kimberlites yield low grade

Bulk sampling has confirmed the low grade of two promising kimberlites at the Fort la Corne joint venture in Saskatchewan.

Pipes 122 and 141 were targeted for additional sampling, the objective being to obtain a sufficient number of macrodiamonds to provide preliminary diamond value estimates for revenue modelling. Kimberlites 122 and 141 are estimated to contain in excess of 540 and 395 million tonnes, respectively, and showed better grade potential for commercial-size stones.

The joint venture comprises: Kensington Resources (KRT-V) and De Beers Consolidated Mines (DBRSY-Q), each of which has a 42.11% stake; Cameco (CCO-T), with 5.78%; and Cameco subsidiary UEM, with 10%.

Three 24-inch, large-diameter reverse-circulation drill holes at kimberlite 122 extracted 328.3 tonnes of sample, from which were recovered 212 stones greater than 1 mm in size, with a combined weight of 17.3 carats. The sample had a preliminary grade of 0.053 carat per tonne, or 5.27 carats per 100 tonnes. Six diamonds larger than half a carat were recovered from the pipe.

A total of 278 diamonds, with a combined weight 21.17 carats, was recovered from 251.8 tonnes of sample from kimberlite 141, for a preliminary grade of 0.084 carat per tonne, or 8.4 carats per 100 tonnes. Eight stones were larger than half a carat, with the two largest stones weighing 1.535 and 1.085 carats.

Based on the bulk-sample results, De Beers has predicted a model grade of 10-16 carats per 100 tonnes for the 122 body and 14-20 carats per 100 tonnes for the 141. Diamond valuations are pending.

The Fort la Corne project comprises 255 sq. km and contains 69 confirmed kimberlite bodies, 49 of which are diamondiferous.