Assessment File Description

The GeologyOntario (includes OGSEarth) web pages will be updated with a new look in the coming weeks, starting at the end of September 2021. The updated design improves the user experience by simplifying the layout, making the pages more mobile compatible, and aligning with other Ministry web pages. Please contact Alphons Evers ( if you encounter any issues after the change or have any questions.


This database is current to September 1, 2021.

The Ontario Assessment File Database (OAFD) comprises geotechnical reports and maps from over 70 years of geological exploration, by mining companies and prospectors, on Crown Land in the Province of Ontario. Since the 1940s, the Government of Ontario has required individuals who perform exploration on claims staked over Crown Land to submit the details of that work, including reports, maps and results, in exchange for the right to retain the claim. Reports contain geoscience data such as airborne geophysics, ground geophysics, geology, geochemistry, diamond drilling and many other geotechnical work types. The OAFD is useful to exploration companies and individual prospectors in their efforts to locate new deposits within the province of Ontario by allowing effective access to past exploration activity reports.

Methods to View/Download Data

The GeologyOntario application provides access to the OAFD through a quick and effective search engine. Searches can be done by using simple keywords or by using focused searches using Boolean operators. Keywords can include the OAFD file number, 2-dot number (2.#####), geographic area (NTS, township), claim holder, performed for, and author. An overview and description of the search types including Boolean can be found on the Help page.

The OAFD can be downloaded from the GeologyOntario application. It is available as a packaged product provided in 2 formats: 1) a relational database and 2) a geospatial GIS (ESRI® shapefile) format. The OAFD captures details on location, property ownership, type of work done and commodities sought for each Assessment File. Spatial data is collected for each file in the form of polygons indicating property outlines that are digitized and displayed on a provincial base map.

The Assessment Work data found on our OGSEarth page can also be viewed in Keyhole Markup Language (KML) format using Google Earth Opens in a new windos or other applications compatible with KML.

Further Information

Further database information and metadata are found within the download package.

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