Osisko Mining
Canadian mineral exploration and gold-development company focused on high-potential projects in Ontario and Quebec.
Last updated August 22, 2026
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Overview
Osisko Mining was a Canadian mineral exploration and gold-development company whose principal objective was to identify and advance a large-scale gold mine in Ontario or Quebec. The company’s modern corporate history began with Oban Mining Corporation, itself created through the 2014 combination of Braeval Mining Corporation and Oban Exploration Limited. Those businesses had mineral interests in South America, but the enterprise later changed direction through a series of mergers and acquisitions that assembled a new Canadian exploration portfolio and reunited members of the management team associated with the earlier Osisko Mining Corporation. The company adopted the Osisko Mining name in 2016 after a 2015 merger involving five exploration companies. Eagle Hill Exploration contributed the Windfall Lake project, which became the company’s central asset and the principal basis for its investment case. Temex Resources contributed royalty interests connected with the Canadian Malartic and Éléonore mines, while Corona Gold and Ryan Gold primarily added cash and securities. John Burzynski became the company’s chief executive during this rebuilding phase. Osisko subsequently expanded its portfolio through the acquisitions of Northern Gold Mining, which brought the Golden Bear project in Ontario, and NioGold Mining Corporation, which brought the Marban project in Quebec. Osisko’s business model was based on mineral exploration, resource definition, technical studies, permitting and project development rather than on a broad portfolio of operating mines. Its activities involved drilling, geological evaluation and the advancement of prospective gold properties toward potential construction and production. Windfall Lake was the flagship project and the company’s main strategic focus. The Golden Bear and Marban properties represented additional exploration and development opportunities, while royalty interests obtained through the Temex transaction provided exposure to producing or advanced Canadian mining assets without being the operator of those mines. The company also participated in portfolio consolidation within the Canadian mining sector. In 2019 it acquired Stornoway Diamond Corporation, obtaining the Renard diamond mine, and its subsidiary O3 Mining acquired Alexandria Minerals Corporation. These transactions broadened Osisko’s asset base beyond its core gold-development focus, although the company remained principally identified with Canadian gold exploration and the Windfall Lake project. Osisko Mining’s independent corporate existence ended when Gold Fields completed its acquisition of the company on October 25, 2024. The transaction was reported at approximately C$1.39 billion. Following completion, Osisko ceased to operate as an independent publicly listed mining company and became part of Gold Fields’ portfolio. Accordingly, the brand is best treated as a defunct or absorbed corporate brand rather than an active standalone issuer. Historical references to Osisko Mining therefore primarily concern the company’s exploration properties, corporate restructuring, acquisitions and the development of Windfall Lake before the Gold Fields transaction.
History
Osisko Mining’s corporate history is rooted in a series of restructurings among Canadian mineral exploration companies. The immediate predecessor of the modern company was Oban Mining Corporation. Oban was formed in 2014 through the merger of Braeval Mining Corporation and Oban Exploration Limited, two Toronto Stock Exchange-listed companies with exploration interests in South America. The resulting company later redirected its strategy toward Canadian assets and the recreation of a management and project platform associated with the earlier Osisko Mining organization. A major step came in 2015, when Oban merged with four other exploration companies: Eagle Hill Exploration, Temex Resources, Corona Gold and Ryan Gold. Eagle Hill contributed the Windfall Lake project, which became the new company’s principal asset and the foundation of its long-term gold-development strategy. Temex added royalty interests linked to the Canadian Malartic and Goldcorp’s Éléonore mine, while Corona Gold and Ryan Gold mainly contributed cash and securities. The transaction consolidated exploration properties, financial resources and management capabilities under one corporate structure. John Burzynski emerged as chief executive during this period. In June 2016, the company changed its name from Oban Mining Corporation to Osisko Mining Corporation. The name signaled the reassembly of an executive and corporate identity connected with the original Osisko Mining Corporation, while the company’s operational emphasis centered on exploration and potential mine development in Ontario and Quebec. The Windfall Lake project became the most important asset in the portfolio, supported by drilling, geological work and the technical evaluation required to determine whether the deposit could support a future mine. The company continued to build its Canadian portfolio through acquisitions. Northern Gold Mining was acquired for its Golden Bear project in Ontario, and NioGold Mining Corporation was acquired for its Marban project in Quebec. These transactions increased Osisko’s exposure to prospective Canadian gold districts and gave the company several properties at different stages of exploration and development. The business remained an exploration and development company rather than a diversified producer with a large operating mine base. Osisko also pursued transactions outside its main gold focus. In 2019, it acquired Stornoway Diamond Corporation, obtaining the Renard diamond mine. Through its subsidiary O3 Mining, it also acquired Alexandria Minerals Corporation. These moves broadened the corporate asset base and reflected the use of acquisitions to consolidate mineral properties and operating or advanced-stage assets. The final major event in the company’s history was its acquisition by Gold Fields. Gold Fields completed the transaction on October 25, 2024, in a deal reported at approximately C$1.39 billion. The completion transferred Osisko Mining into Gold Fields and ended its status as an independent listed exploration and development company. Its historical significance now rests mainly in the corporate assembly that created the Windfall Lake-focused platform, the advancement of Canadian gold properties, and the eventual sale of that platform to a major international gold producer.
- 2024
Gold Fields completes acquisition
[1]Gold Fields completed its acquisition of Osisko Mining on October 25, ending Osisko’s independent corporate and listed-company status.
- 2019
Stornoway Diamond Corporation acquisition
[1]Osisko acquired Stornoway Diamond Corporation and added the Renard diamond mine to its portfolio.
- 2016
Oban Mining adopts the Osisko Mining name
[1]The company changed its name to Osisko Mining Corporation after the merger-led reassembly of the business and its management team.
- 2015
Five-company merger assembles the new Osisko platform
[1]Oban combined with Eagle Hill Exploration, Temex Resources, Corona Gold and Ryan Gold. Eagle Hill contributed the Windfall Lake project, which became the principal asset.
- 2014
Oban Mining Corporation is formed
[1]Braeval Mining Corporation and Oban Exploration Limited merged to create Oban Mining Corporation, the corporate predecessor of modern Osisko Mining.
Products and positioning
A Canadian exploration and development platform focused on advancing high-potential gold properties in Ontario and Quebec, particularly the Windfall Lake project.
Gold exploration and development project · 2015
Windfall Lake
Windfall Lake was the company’s principal gold project and the central asset inherited through the Eagle Hill Exploration merger. Osisko’s strategy was to advance the property through exploration, drilling, resource definition and technical evaluation with the long-term aim of developing a mine in Quebec. The project provided the core of the company’s identity and investment proposition until its acquisition by Gold Fields.
Gold exploration and development project
Marban
The Marban project in Quebec entered Osisko’s portfolio through the acquisition of NioGold Mining Corporation. It represented an additional Canadian gold exploration and development opportunity alongside Windfall Lake and formed part of the company’s broader Quebec-focused property base.
Gold exploration project
Golden Bear
The Golden Bear project in Ontario was obtained through Osisko’s acquisition of Northern Gold Mining. It complemented the company’s Quebec properties with an Ontario exploration asset and supported its strategy of assembling a portfolio of prospective Canadian gold projects.
Mining royalties · 2015
Canadian Malartic and Éléonore royalty interests
Through the 2015 merger with Temex Resources, the company obtained net smelter return royalty interests associated with the Canadian Malartic mine and Goldcorp’s Éléonore mine. These interests provided indirect economic exposure to Canadian mining operations rather than representing mines operated directly by Osisko.
Diamond mine · 2019
Renard diamond mine
The Renard diamond mine was added through Osisko’s 2019 acquisition of Stornoway Diamond Corporation. It broadened the company’s holdings beyond gold and gave Osisko ownership of an operating or advanced diamond asset during its later independent history.
Brand decisions
2024
Sale to Gold FieldsM&ABackground
Gold Fields pursued ownership of Osisko Mining and its Canadian exploration and development portfolio, including the Windfall Lake project.
Action taken
Gold Fields completed the acquisition of Osisko Mining on October 25, 2024, in a transaction reported at approximately C$1.39 billion.
Aftermath
Osisko ceased to be an independent publicly listed company and became part of Gold Fields’ portfolio.
Acquisition value. C$1.39 billion (Completed October 25, 2024)
2019
Acquisition of Stornoway Diamond CorporationM&ABackground
Osisko sought to broaden its mineral portfolio and acquire the Renard diamond mine through the purchase of Stornoway Diamond Corporation.
Action taken
Osisko acquired Stornoway Diamond Corporation and added Renard to its assets.
Aftermath
The transaction diversified Osisko beyond its primary gold exploration and development activities.
2016
Rebrand from Oban Mining to Osisko MiningStrategyBackground
The company had been rebuilt through mergers involving several exploration businesses, including Eagle Hill Exploration, whose Windfall Lake project became the principal asset. The rebrand reflected the reassembly of an Osisko-associated management and corporate platform.
Action taken
Oban Mining Corporation changed its name to Osisko Mining Corporation in June 2016.
Aftermath
The renamed company continued as a Canadian exploration and development business focused primarily on Windfall Lake and other Ontario and Quebec properties.
Recent events
- 2024
Gold Fields completes acquisition of Osisko Mining[1]
M&A
Gold Fields completed its acquisition of Osisko Mining, ending Osisko’s existence as an independent publicly listed mining company.
- 2019
Osisko Mining acquires Stornoway Diamond Corporation[1]
M&A
Osisko acquired Stornoway Diamond Corporation, adding the Renard diamond mine and expanding its portfolio beyond gold exploration.
- 2016
Osisko Mining changes its corporate name after merger-led restructuring[1]
Other
The company formerly known as Oban Mining Corporation adopted the Osisko Mining name after a sequence of mergers that assembled the Windfall Lake-focused exploration business.
Sources4 sources
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