The company has completed 12,010m of deep directional drilling at the Renard 2 kimberlite from three pilot holes and identified deeper kimberlite at 1,012m below surface.
Considering dimensions of the Renard 2 at 600m depths with dimensions in the upper portion of the pipe, the tonnage range is estimated at 9 to 12 million tons between 600m and 1,000m depth.
Stornoway Diamond president and CEO Matt Manson said: "Whilst the kimberlite clearly shows areas of gentle pinching and swelling with depth, at 1,000 meters below surface it is still of a size and geological composition comparable to what we see closer to the surface.
"This is a remarkable ore body, and the 2014 drill program, which has been technically challenging to complete, has succeeded in delineating many years of potential mining beyond the current 11 year reserve based mine plan.
"We now move into the detailed geological modeling and sample processing work, with a revised Mineral Resource estimate expected at the end of Q2 2015."
Drilling on the Renard 2 started in early April with three drill rigs establishing a single pilot hole each from which a series of constrained branches were cut using directional drilling equipment.
In total, 33 branches were cut from the three pilot holes ranging in length from 5.3m to 724.8m.
