- NI 43-101 is the Canadian disclosure standard for mineral projects, and it defines specific resource and reserve categories.
- Resources (inferred, indicated, measured) describe what is in the ground; reserves (probable, proven) describe what is economically mineable.
- Higher confidence categories require more drill data and more rigorous engineering.
What is NI 43-101?
National Instrument 43-101 is the disclosure standard adopted by Canadian provincial and territorial securities regulators for mineral projects. It governs what a reporting issuer can say about a mineral deposit and requires a Qualified Person to approve all technical disclosure.
Mineral resources vs mineral reserves
Mineral resources describe mineralized rock that may have reasonable prospects for eventual economic extraction. Mineral reserves are the portion of a measured or indicated resource that has been demonstrated to be economically mineable in a feasibility-level study. All reserves come from resources; not all resources become reserves.
The resource categories
Inferred resources are based on limited sampling and assumed continuity. Indicated resources are based on sampling close enough to confirm geological and grade continuity. Measured resources have the highest confidence and are based on detailed sampling, typically at close spacing.
The reserve categories
Probable reserves are the economically mineable part of indicated (and sometimes measured) resources. Proven reserves are the economically mineable part of measured resources, with the highest confidence.
Why category matters for investors
Resource category drives confidence and is reflected in mine planning. Banks financing a mine generally require reserves in the proven and probable categories. A resource with mostly inferred tonnes is a different investment proposition than one with mostly measured and indicated tonnes.
| Category | What it is | Confidence level |
|---|---|---|
| Inferred resource | Limited drilling, geology-driven extrapolation | Lowest |
| Indicated resource | Drill density sufficient for continuity | Medium |
| Measured resource | Close-spaced drilling and sampling | Highest among resources |
| Probable reserve | Economically mineable indicated material | Bank-financeable |
| Proven reserve | Economically mineable measured material | Highest |
Definitions follow National Instrument 43-101 and the CIM Definition Standards for Mineral Resources and Mineral Reserves.
Frequently asked questions
Definitions follow National Instrument 43-101 and the CIM Definition Standards for Mineral Resources and Mineral Reserves.
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