Greenstone struck an agreement with the Aroland First Nation, Animbiigoo Zaagi'igan Anishinaabek and Ginoogaming First Nation.
Greenstone GM Eric Lamontagne hailed the pact as an important milestone.
The agreement formalises the partnership's commitment towards protecting the environment and supporting the local First Nations social and cultural practices, and provides for environmental monitoring, employment, training, business and contracting opportunities.
Hardrock hosts measured and indicated resources of 7.1 million ounces gold, with some 5.9Moz seen to have openpit mining potential.
The partners aim to be able to make a build decision on Hardrock by the end of 2019. All the permits are in place to start construction by mid-2020.
Greenstone proposes development of an openpit mine that could produce on average 300,000oz/y over a 14.5-year mine life.