DIAMOND PAGE — Ashton continues work at Buffalo Hills

The final three of nine kimberlites discovered last winter on the Buffalo Hills project in north-central Alberta have proved to be barren.

Only one micro (less than 0.5 mm) was recovered from the K-32 kimberlite, while K-93 and K-15 yielded no diamonds. These three kimberlites are part of a separate cluster 30 km southeast of the K-14 complex.

In all, Ashton Mining of Canada (ACA-T) has uncovered 23 kimberlites on the original 1.4-million-acre Buffalo Hills project since January 1997. Sixteen of these kimberlites have proved diamondiferous, with four (K-14, K-91, K-5 and K-6) having undergone mini-bulk sampling.

The K-14 complex was initially interpreted as being three separate kimberlites, but delineation drilling now suggests it is a single large kimberlite complex measuring 400 metres in diameter. The complex comprises a central pipe that is open to depth and flanked by a thick apron of tuffisitic crater facies kimberlite extending to the north and northeast.

A 44.87-tonne composite sample of the K-14 complex, collected from surface pits, yielded 7.79 carats of diamonds larger than 0.8 mm in size, giving a preliminary grade of 17.4 carats per 100 tonnes.

The seven largest stones weigh a collective 3.2 carats, representing 41% of the total weight. The largest diamond, a 1.31-carat stone, was described as “a single crystal, of silver-grey appearance, with many dark inclusions.” The other six stones are said to be generally clear.

Ashton says the results indicate the presence of commercial-size stones, while adding that diamond content varies greatly in samples collected over relatively short distances.

As part of the 1998 winter program, Ashton collected an additional 450-tonne bulk sample from the K-14 complex using reverse-circulation drill rigs. That sample is waiting to be processed.

The installation of a 10-tonne-per-hour, modular dense media separation plant at Buffalo Hills is not expected to begin until late summer or early fall. In the meantime, Susan Morrison, a spokesman for Ashton, says the company continues to look for an outside contract plantcapable of processing the sample more quickly.

Meanwhile, the processing of a 40-tonne mini-bulk sample from the K-91 kimberlite at Ashton’s North Vancouver recovery plant is nearing completion.

Results are expected by the end of July. The K-91 kimberlite lies 2.3 km northwest of the K-14 complex.

Microdiamond testing in late 1997 showed that this body has one of the highest counts among the Buffalo Hills kimberlites, yielding 12 macros (+5 mm) and 180 micros from a 117-kg sample. The remaining samples from the initial drilling were processed by dense media separation. A 0.301-carat parcel exceeding 0.8 mm in size was recovered from a 0.85-tonne sample, giving a preliminary grade of 35.4 carats per 100 tonnes. The two largest stones recovered weighed 0.14 and 0.13 carat, representing 90% of the total weight.

David James, a mining analyst with Canaccord Capital, cautions that it is unlikely that stones under 1.5 mm would be commercially recovered and that it is therefore too early to draw any conclusions as to the grade indicated by this small sample.

Mini-bulk samples taken from kimberlites K-5 and K-6 were previously reported. A 7.55-tonne sample of K-5 yielded 0.03 carat of diamonds, resulting in a preliminary grade of 0.397 carat per 100 tonnes.

A parcel weighing 0.876 carat was recovered from an aggregate 13.95-tonne sample of kimberlite K-6, equating to a preliminary grade of 6.28 carats per 100 tonnes. The diamonds recovered from K-6 included a clear, yellow stone weighing 0.76 carat.