JORC Resource Estimates Explained: Reading Australian Mining Disclosure

Summary box

• The JORC Code 2012 is the reporting standard for ASX-listed mining companies. It supersedes the 1989, 1992, 1996, 1999 and 2004 editions.
• Australia says Ore Reserve where Canada and the United States say Mineral Reserve. The concept is the same.
• JORC uses Competent Person where NI 43-101 and S-K 1300 use Qualified Person.
• Inferred Mineral Resources have no direct link to any category of Ore Reserve. Measured can become Proved or Probable; Indicated can only become Probable.
• Table 1 is the checklist that turns a JORC report from a claim into an auditable document. Almost nobody reads it. It is where the real disclosure lives.

What JORC is

The Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves — the JORC Code — is maintained by the Joint Ore Reserves Committee, established in 1971. As the Code itself records, JORC "published several reports containing recommendations on the classification and Public Reporting of Ore Reserves prior to the release of the first edition of the JORC Code in 1989. Revised and updated editions of the Code were issued in 1992, 1996, 1999, and 2004. This 2012 edition supersedes all previous editions."

It is incorporated into the ASX Listing Rules, so compliance is not voluntary for listed issuers.

JORC also sits at the origin of the international family of codes. Since 1994 the Committee for Mineral Reserves International Reporting Standards (CRIRSCO) has worked "to create a set of standard international definitions for reporting Mineral Resources and Mineral (Ore) Reserves, based on the evolving JORC Code's definitions." That shared ancestry is why Canadian, Australian, South African and US categories translate almost one-to-one.

The classification framework

Mineral Resources are reported as Inferred, Indicated or Measured, in ascending order of geological confidence. JORC defines an Indicated Mineral Resource as one where quantity, grade, densities, shape and physical characteristics "are estimated with sufficient confidence to allow the application of Modifying Factors in sufficient detail to support mine planning and evaluation of the economic viability of the deposit."

Ore Reserves are reported as Probable or Proved. The Code is explicit that Ore Reserves "are a modified sub-set of the Indicated and Measured Mineral Resources" and "require consideration of the Modifying Factors affecting extraction."

On the conversion rules, JORC states plainly:

"Measured Mineral Resources may be converted to either Proved Ore Reserves or Probable Ore Reserves."

and, for the lower category:

"there is no direct link from an Inferred Mineral Resource to any category of Ore Reserves"

An Indicated Mineral Resource "may only be converted to a Probable Ore Reserve." Confidence can be downgraded during conversion — a Competent Person may take Measured material to Probable if the Modifying Factors are less certain — but it can never be upgraded.

Modifying Factors, defined

The Code gives the term a precise meaning:

"'Modifying Factors' are considerations used to convert Mineral Resources to Ore Reserves. These include, but are not restricted to, mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social and governmental factors."

Ten factor families. A reserve is a resource that has survived all of them. When a project's reserve is much smaller than its resource, the answer to "why" is always in this list — most often mining (pit shell or stope design), economic (price and cost), or legal/governmental (permitting and tenure).

The Competent Person

JORC's analogue to the Qualified Person is the Competent Person: a minerals industry professional who is a member of a recognised professional organisation, bound by enforceable rules of conduct, with sufficient relevant experience in the style of mineralisation, the type of deposit and the activity being undertaken.

Two practical checks:

1. **Is their experience relevant to this deposit type?** Competence in iron ore does not transfer automatically to a lithium brine or an epithermal gold vein.
2. Is consent on file? The Code requires that a Public Report be based on, and fairly reflect, information compiled by a named Competent Person who has given written consent to the form and context in which it appears. A report naming no Competent Person is not a JORC report.

Table 1: where the disclosure actually is

Table 1 is a structured checklist appended to JORC public reports, organised in four sections that build on one another:

• Section 1 — Sampling Techniques and Data. Sampling method, drilling technique, sample recovery, logging, sub-sampling, assay quality, verification, location surveying, data spacing, orientation of data relative to structure, sample security, audits.
• Section 2 — Reporting of Exploration Results. Tenure and land status, historical work by other parties, geology, drill-hole information, data aggregation methods, relationship between mineralisation widths and intercept lengths, diagrams, balanced reporting.
• Section 3 — Estimation and Reporting of Mineral Resources. Database integrity, geological interpretation, dimensions, estimation methodology, moisture, cut-off parameters, mining and metallurgical assumptions, environmental factors, bulk density, classification, audits, discussion of relative accuracy.
• Section 4 — Estimation and Reporting of Ore Reserves. Modifying Factors in detail: mine plan, dilution, mining recovery, infrastructure, costs, revenue factors, market assessment, economic inputs, social licence, permitting.

Table 1 operates on an "if not, why not" basis: where a criterion is not addressed, the Competent Person is expected to explain why it is not relevant. That makes Table 1 the most efficient audit tool in Australian mining disclosure. Two specific lines repay attention every time:

• "Relationship between mineralisation widths and intercept lengths" — this is where true width versus downhole width is disclosed or explicitly dodged.
• "Discussion of relative accuracy/confidence" — where the Competent Person states, in words, how wrong the estimate could be.

JORC against the other codes

The two spelling differences — Proved/Proven, Ore Reserve/Mineral Reserve — are a data-mapping problem, not an economic one. If you maintain a cross-exchange dataset and do not normalise them, your Australian reserves will silently fall out of every query.

JORC also places specific restrictions on publishing production targets and forecast financial information derived from Scoping Studies or from Inferred Mineral Resources. The Code cautions directly that "Caution should be exercised if Inferred Mineral Resources are used to support technical and economic studies such as Scoping Studies." An ASX release attaching an NPV to a study heavy in Inferred material carries mandatory cautionary language — read it rather than skipping it.

Reading an ASX resource announcement

• [ ] Competent Person named, with organisation and consent
• [ ] Resource table split by category, with a stated cut-off grade
• [ ] Metal price and recovery assumptions behind the cut-off
• [ ] Whether resources are inclusive or exclusive of Ore Reserves
• [ ] Effective date, and depletion since if the mine is producing
• [ ] Table 1 attached, and Section 1 sampling criteria actually completed
• [ ] Mineralisation width versus intercept length addressed
• [ ] For any production target or financial forecast: the proportion of Inferred material and the cautionary statement
• [ ] Comparison to the previous estimate, with the change explained

How Mining Terminal handles JORC data

Mining Terminal ingests ASX filings alongside SEDAR+, EDGAR, LSE and other exchange feeds, and normalises JORC categories against CIM and S-K 1300 so a cross-exchange peer set is genuinely comparable. Proved is mapped to Proven and Ore Reserve to Mineral Reserve at the data layer, with the source terminology retained on the record so nothing is lost.

Cut-off grade, price assumption, effective date and Competent Person attribution are carried with each estimate. Where a filing does not disclose one of them, the field stays empty rather than being inferred from a sibling document.

To compare JORC and NI 43-101 resources on one axis, get in touch or ask Nara.

Related reading

• Mineral Reserves vs Mineral Resources
• How to Read an NI 43-101 Technical Report
• Cut-Off Grade Explained

Sources

• The JORC Code, 2012 Edition, including Table 1 — Joint Ore Reserves Committee
• JORC — jorc.org
• CIM Definition Standards, 10 May 2014 — BCSC-hosted copy
• National Instrument 43-101 — Ontario Securities Commission

This article is educational and is not investment advice. Mining Terminal is a data platform, not a broker, dealer or investment adviser.