Ontario has been the target of focused diamond exploration for nearly four decades. Interest dates back to the 19th century when diamonds were found in glacial deposits in southern Ontario, Michigan, Wisconsin and Illinois. The source of the diamonds was suspected to be Ontario, most likely northern Ontario.
During the late 1940s, a government geologist identified a thin intersection of kimberlite in old diamond drill core near Kirkland Lake. Exploration for the bedrock source did not develop in earnest until the 1960s when kimberlite indicator minerals were found in esker sediments. This led to the discovery of a kimberlite dike in the area and, later in the 1980s, the first kimberlite pipes were found in the province through the use of indicator minerals and geophysical invetigations.
Much of the current diamond exploration in Ontario is focused in the James Bay-Hudson Bay Lowlands, Wawa, Cobalt to Kirkland Lake, and The northern extent of the Ontario-Manitoba border.
Work conducted by the Ontario Geological Survey (OGS) has highlighted diamond potential in several areas of Ontario, including Wawa, Kapuskasing, River Valley, Temagami, Marathon, Kirkland Lake and northwest Ontario. Recently the OGS has focused on the Kapuskasing-Wawa, Marathon, River Valley and Temagami to North Bay areas. This work supplements previous diamond studies by the OGS in the Kirkland Lake area. OGS staff members are involved in a province-wide evaluation of kimberlite.
Under Operation Treasure Hunt, the OGS is overseeing kimberlite indicator mineral studies for the zone stretching from Wawa to southwest of Moosonee, from Sault Ste. Marie to Espanola, and in portions of the James Bay Lowland. In collaboration with the Geological Survey of Canada and Industry Canada, the OGS conducted a geophysical airborne survey over the area between Chapleau and Kapuskasing that is inferred to have diamond potential.
—Mary Rocca and Peter Cashin, Ontario Ministry of Northern Development & Mines