It increased the grades and ounces at Lynx compared with a May estimate, to an indicated 1.7 million tonnes at 8.13g/t gold for 456,000 ounces and an inferred 2Mt at 9.7g/t for 625,000oz.
The resource update increases the global Windfall resource to an indicated 754,000oz averaging 8.17g/t and an inferred 2.4Moz averaging 7.11g/t.
"Osisko's Lynx discovery now represents over 1Moz of the global resource, and we are confident that as we complete the infill drilling we will continue to see the average indicated grade move up," president and CEO John Burzynski said.
The company plans to update the Windfall resource in 2019. It has an 800,000m programme underway and is drilling at its recent Triple 8 discovery.
"Osisko remains well financed as one of the most aggressive gold explorers in the business," Burzynski said.
The company raised C$25 million (US$19 million) through a private placement this month at $2.70 per share to institutional investor la Caisse de dépôt et placement du Québec, to continue developing Windfall.
It had closed a $76.4 million (US$58.4 million) raising about six weeks earlier, issuing flow-through shares at $2.30 and $2.85 and common shares at $1.70.
Burzynski said Osisko was expecting the initial results from its Zone 27 bulk sampling next month.
A preliminary economic assessment released in July for Windfall, including the satellite Osborne-Bell deposit, put preproduction capex at C$397.3 million with an after-tax IRR of 32.7% for an 8.1-year mine producing an average 218,000oz a year.
Shares in the company, which were trading above $3.70 a year ago, closed down 3c yesterday to $2.50 to value it close to $642 million.