A 469-tonne bulk sample of the Hearne kimberlite pipe in the Northwest Territories has yielded 846 carats, for an average grade of 1.8 carats per tonne.
The pipe is on the AK property, which, together with the CJ claims, is a joint venture among Monopros,
The AK property is 320 km northeast of Yellowknife and 115 km southeast of Lac de Gras.
Bulk sampling of the 5034, Hearne, Tuzo and Tesla pipes began in January and was completed in April. Kimberlite was extracted using reverse-circulation drills and processed at Monopros’s dense media separation plant at Grand Prairie, Alta. The resulting concentrates were shipped to Johannesburg, South Africa, where the diamonds were recovered. A 1.5-mm square screen was used as the bottom cutoff size.
Monopros drilled a total of 10 holes into the Hearne kimberlite to depths ranging from 155 to 300 metres. The pipe consists of two bodies: the main body, which measures more than 300 metres in length in a north-southerly direction; and the second, which lies just south of the main body and measures up to 80 metres long in an east-westerly direction.
The grade per hole ranged from 1.05 carats to 3.01 carats per tonne, and the largest two diamonds recovered weighed 3.37 and 3.16 carats. In total there were nine diamonds greater than two carats, 40 greater than one carat, 90 weighing between half a carat and one carat, and 599 between one-fifth of a carat and half a carat.
By comparison, the largest diamond recovered in last year’s 62.6-tonne test sample weighed 1.87 carats. From that sample, Monopros modelled a grade of 2.33 carats per tonne using a 1.5-mm square cutoff size. A best-fit value of US$44 per carat was estimated.
The diamonds from the latest bulk sample are in Kimberly, South Africa, and will be valued after undergoing an acid cleansing. Results are expected later this summer.
Monopros says the modelled grade (2.33 carats per tonne) was observed in all drill holes and was consistent within vertical intervals that ranged from about 50 metres to 285 metres in length. A few of the holes contained grades lower than the modelled average. These lower-grade intervals ranged up to 100 metres. Preliminary analysis indicates that these lower-grade sections correlate with a specific geological zone in the main kimberlite. This zone is at the center of the pipe, near the surface, and plunges steeply towards the north. The southern part of the pipe does not appear to have this lower-grade zonation pattern. Interpretation of sample results and geological data is ongoing. De Beers intends to produce a refined grade estimate, based on three-dimensional modelling, which will distinguish between different geological zones.
Bulk-sample results from the Tuzo and Tesla pipes are pending.
Be the first to comment on "Bulk sample results add lustre to Hearne pipe in NWT"