Canadian miner Mountain Province Diamonds has published Phase 1 drilling results for the discovery, as reported in July, of the Hearne Northwest Extension at the Gahcho Kué mine.

The Hearne kimberlite is one of four kimberlites being mined at Gahcho Kué mine, which is presently ranked as fourth globally in terms of yearly diamond production. Mountain Province is a 49% shareholder at Gahcho Kué, with joint venture (JV) partner De Beers Canada, with a 51% interest, being the operator of the mine.

The Hearne Northwest Extension was first visually identified in late 2021, when kimberlite measuring 25 m across in a bench face was exposed during routine mining operations. A discovery drilling programme was subsequently launched with initial results reported earlier this year.

Ground-based geophysics initially suggested a west-northwest direction for the extension, but a northwest direction has been confirmed from the Phase 1 drilling.

Phase 1 drilling of the Hearne Northwest Extension includes 16 drillholes totalling 5 040 m. Ten of the sixteen drillholes have significant kimberlite intersections that have been used to model this large extension.

Completion of the Phase 1 drilling and subsequent modelling of the data suggests that a significant volume of kimberlite may be present.

“The latest results generated with our operating partner De Beers suggest that the Hearne Northwest Extension is a significant discovery, potentially equal in volume to the Hearne orebody as it was originally defined.

“As the extension is only in the exposed lower benches of the openpit and plunges to the northwest, an underground operation to recover this ore is a logical pursuit, and the Gahcho Kué JV is actively reviewing underground options for economic recovery of this material,” says Mountain Province CEO and president Mark Wall.

Further logging, petrography, mineral chemistry and microdiamond analysis is also underway to properly define the internal HK and TK lithologies in the extension and its relationship to the main Hearne kimberlite.

A second phase of drilling will be required to define the volume and depth extent of the northwest extension and its economic viability for extraction by underground mining methods.