Harte said the new mineral resource estimate included 2.607 million tonnes grading 8.52 grams per tonne (714,200oz) and inferred 3.59Mt at 6.59gpt (760,800oz) at a 3gpt cut-off grade, compared with its 2012 NI 43-101 indicated resource of 1.11Mt at 8.41gpt (302,000oz) and inferred 417,000t at 7.13gpt (95,000oz).

The updated resource would form the basis of the new PEA, along with "operating inputs" derived from extraction of 100,000t from underground in sampling and commercial programs.

The company plans to complete 30,000m of infill drilling on the project's Sugar and Middle zones this year. It said this week about half the new indicated resource was in the top 500m of the main zones, and it "believes the gold grade is continuous at depth and will improve as infill drilling continues".  

Harte CEO and president Stephen Roman the resource upgrade was based largely on 2017 drilling.

"With the Middle Zone discovery and the extension of the Sugar Zone down dip we have now delineated 1.5 million ounces and have demonstrated this deposit has significant size potential," he said.

"As we have been mining at the Sugar Zone property for the last two years, we have confirmed the grade, continuity and mining method. We will continue to develop this mineral resource at depth and along strike.

"With all major capital components either paid or contracted, project economics are well defined. Process plant construction is on schedule and we expect to start commissioning by the beginning of H2 2018."

Harte shares were down 10.6% on the news Thursday. The company's current market capitalisation is C C$234.9 million.