The Stewardson magnetite occurrence is located on the southern shore, near the entrance to Stewardson Inlet.
The area is underlain by granodioritic rocks of the Jurassic Island Plutonic Suite (Geological Survey of Canada Map 1537A).
Locally, a south west striking band of amphibolite, approximately 200 metres wide, is in contact with granitic rocks of the Jurassic Island Plutonic Suite. It is dark green to black in colour and consists of amphibole, plagioclase and magnetite. A selected sample assayed 10.92 per cent iron (Assessment Report 462).
In 1962, Paco Resources completed a program of geological mapping on the area.