What Is JORC in Mining? How to Read a Resource Table

JORC stands for the Joint Ore Reserves Committee. In mining it also means the committee’s rulebook, the JORC Code, which sets the minimum standard for how a company tells the public about exploration results, mineral resources and ore reserves. The first Code appeared in February 1989 and was written into the ASX listing rules straight away (JORC Committee, development of the Code). The 2012 edition has been mandatory since 1 December 2013, and a replacement was still being finalised in August 2026 (JORC webinar slides, 20 August 2026). This page explains the terms in plain English, decodes a real company resource table line by line, compares JORC with the Canadian and US rules, and shows what a satellite screen can and cannot say.

What does JORC stand for in mining?

JORC is short for the Australasian Joint Ore Reserves Committee. The full title of its rulebook is the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves. The committee was set up in 1971 and is backed by three parent bodies: the Minerals Council of Australia, the Australasian Institute of Mining and Metallurgy (AusIMM) and the Australian Institute of Geoscientists (AIG) (JORC Committee).

The story starts in the late 1960s. The Poseidon nickel boom and bust in Western Australia raised concern about unacceptable reporting practices, and the industry decided to regulate its own reporting. The idea of the Competent Person, a named and qualified professional who stands behind the numbers, appeared in JORC’s first publication in 1972 (JORC Committee history).

Two things make the Code binding. The ASX and the New Zealand exchange (NZX) wrote it into their listing rules, in 1989 and 1992, and AusIMM and AIG members must follow it (JORC Code, 2012 Edition). Under ASX Listing Rule 5.6, any public report that mentions exploration targets, exploration results, mineral resources or ore reserves must follow rules 5.7 to 5.24 and the Code (ASX Listing Rules, Chapter 5). A “public report” is wide: it includes press releases, annual reports, website pages and investor slides.

The Code rests on three principles. Transparency means the reader gets clear information and is not misled by omission. Materiality means the report contains everything an investor would reasonably expect to find. Competence means the work is the responsibility of suitably qualified people who are bound by an enforceable code of ethics. It also helps to know what the Code is not. It does not tell a geologist how to estimate a resource; it governs how the result is reported.

The six JORC categories side by side

Every JORC number sits in one of six boxes. The first four describe how well the ground is known (geological confidence). The last two describe whether the material has been shown to be worth mining, using what the Code calls Modifying Factors: mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social and governmental considerations.

Infographic

From exploration result to ore reserve in 5 steps

1. 1Exploration ResultsSampling, mapping and drilling data; no tonnage or grade estimate is given.
2. 2Inferred resourceLimited evidence implies, but does not prove, continuity of the mineralisation.
3. 3Indicated resourceEnough data to assume continuity and to support mine planning.
4. 4Pre-feasibility or feasibility studyApplies the Modifying Factors: mining, processing, costs, legal, environmental and social.
5. 5Probable or Proved reserveThe economically mineable part of the Indicated or Measured resource.

The definitions come from clauses 17 and 20 to 31 of the Code (JORC Code, 2012 Edition). Two details catch readers out. First, every resource, whatever its category, must pass the test of “reasonable prospects for eventual economic extraction”, which the Code glosses as more likely than not. Ground that fails the test stays out of the resource. Second, an ore reserve includes the diluting waste and the losses that happen in mining, so it is smaller than the resource it comes from. Our guides to mineral resource estimation and ore reserve estimation methods show how the numbers behind each category are built.

How to read a JORC resource table in 5 steps

The best way to learn the Code is to read a real statement. Northern Star Resources (ASX: NST) published its annual statement on 3 June 2026, with figures as at 31 March 2026 (Northern Star ASX announcement, 3 June 2026). It reports a group Mineral Resource of 1,617 million tonnes (Mt) at 1.7 grams per tonne (g/t) for 88.9 million ounces (Moz) of gold, and an Ore Reserve of 627 Mt at 1.4 g/t for 28.4 Moz. The steps below use it as the worked example.

Chart

Northern Star gold resource by confidence category

Million ounces (Moz), 88.9 Moz total at 31 March 2026, inclusive of reserves

1. Find the edition and the signature. The statement says it is aligned to the 2012 edition of the Code and names the Competent Persons who take responsibility, with their institute and employer. A report that gives new or materially changed results without naming anyone is missing something clause 9 requires.
2. Separate resource from reserve. Northern Star states that its resources are inclusive of reserves. So the 28.4 Moz reserve sits inside the 88.9 Moz resource. Adding the two would count the same gold twice. Some companies report resources exclusive of reserves, so always check the footnote for the basis.
3. Look at the confidence split. Of the 88.9 Moz, 5.6 Moz is Measured, 47.6 Moz is Indicated and 35.7 Moz is Inferred. Inferred ounces are about 40% of the total and, under the Code, cannot be turned into reserves.
4. Check that tonnes times grade gives ounces. 1,617 Mt at 1.7 g/t works out to about 88 Moz before rounding, which matches. The calculator below does this sum for any table. A large gap means a rounded grade or a typo.
5. Read the price and cut-off assumptions. Northern Star uses A$3,700 per ounce for resources and A$2,900 per ounce for reserves (Pogo, in Alaska: US$2,600 and US$1,900). The reserve price is lower than the resource price, and a reserve also allows for dilution, mining losses and costs, so it is much smaller than the resource.

The same logic applies to other metals, with the grade in percent instead of grams per tonne. In IGO’s February 2026 release on the Greenbushes lithium mine in Western Australia, the total resource is 457 Mt at 1.6% lithia (Li2O), while the open-pit ore reserve is 176 Mt at 1.9% (IGO, Greenbushes CY25 estimates, 12 February 2026). IGO released it because the estimates had changed materially, which is what ASX Listing Rules 5.8 and 5.9 require: a fresh announcement whenever a resource or reserve is reported for the first time or changes materially.

Check a resource table’s arithmetic

Contained metal is tonnes times grade, divided by 31.1035 to convert grams to troy ounces. Any gold resource statement can be tested in seconds, and the same calculator shows the gross value of the recovered gold at a price you choose. Rounded grades make small differences, so a gap of a few per cent is normal; a gap of 20 per cent is a question for the company. The chart shows how far a resource shrinks on the way to a reserve in the Northern Star table: KCGM goes from 42.2 Moz of resource to 15.0 Moz of reserve, Hemi from 13.2 Moz to 5.5 Moz and Pogo from 9.3 Moz to 2.4 Moz.

Chart

Resource versus reserve in three Northern Star projects

Million ounces of gold at 31 March 2026 (resources are inclusive of reserves)

▶ Shows how a satellite image becomes a tonnage and a grade, and which inputs are measured and which are assumed. · 2:54

Why resource numbers change from year to year

A JORC number is an estimate at a date, not a measurement. Northern Star’s group resource rose from 70.7 Moz to 88.9 Moz in the year to 31 March 2026, an increase of 18.2 Moz (26%) after mining depletion. The largest single item is the Hemi project in Western Australia, which was included for the first time and added 13.2 Moz after Northern Star acquired De Grey Mining in May 2025. The Kalgoorlie centre added 3.6 Moz, mostly at the KCGM mine (+3.3 Moz), where drilling at Fimiston Underground extended lodes. Pogo in Alaska added 3.1 Moz from new drilling and a lower cut-off grade (from 4.1 g/t to 3.4 g/t) at a higher price assumption. Against that, the Yandal centre lost 0.4 Moz to depletion and smaller pits, and the divestment of the Central Tanami joint venture removed 1.3 Moz. The company states that its higher gold price assumptions (A$3,700 per ounce for Australian assets, up from A$3,000; US$2,600 for Pogo, up from US$2,000) have no material impact on group resources.

Chart

Northern Star group gold resource over time

Million ounces (Moz) at selected statement dates: 30 June 2014 to 2020, 31 March from 2022. Dates are unevenly spaced: two-year steps to 2024, then yearly

Four things move a resource, and Northern Star’s bridge shows all of them. New drilling adds or removes ounces. Changes in the price or cost assumptions change the cut-off grade (the lowest grade still counted as worth mining). Acquisitions add whole projects. And mining removes ounces, called depletion. When you compare two years, ask which of the four caused the change. For a longer view, the chart shows Northern Star’s reported group resource at selected statement dates, from the 30 June 2014 statement to the 31 March 2026 one.

Who is a Competent Person, and how to choose a JORC consultant

The Code defines a Competent Person as a minerals industry professional who is a Member or Fellow of AusIMM, of AIG or of a Recognised Professional Organisation on the JORC and ASX list. These bodies must have enforceable disciplinary processes. The person needs at least five years of relevant experience in the style of mineralisation and in the activity being signed: exploration for exploration results, estimation for resources, and estimation plus economic extraction for reserves (JORC Code, 2012 Edition, clause 11).

Under clause 9 the company, through its board, owns the public report. It must name the Competent Person, say whether they are a full-time employee (and if not, name the employer), disclose any conflict of interest, and obtain their prior written consent to the form and context of the published text. ASX Listing Rule 5.22 repeats the naming and consent requirements for market announcements and adds the name of the professional organisation the person belongs to. In practice you will see this as a short paragraph at the end of an announcement, as in the Northern Star example, where each statement gives the person’s name, institute membership and employer.

Many juniors hire an outside consultant for a first resource. The Code does not require independence, but it requires the relationship to be disclosed. When you compare consultants, ask for:

• the resources they have signed for the same style of deposit (vein gold, porphyry copper, lithium pegmatite and so on), because “relevant” experience is the test in the Code;
• their professional membership, which you can check with AusIMM or AIG;
• a written scope that names the stage (exploration results, resource or reserve), the data they will review and the site visit;
• how they handle gaps in sampling quality control, since late rework is the usual cause of cost overruns.

There is no standard price list. The cost follows the stage, the condition of your database, the number of domains in the deposit and the travel involved, so get quotes against a written scope. For more on the consultant market, see our guide to JORC reports, Table 1 and Competent Persons.

JORC, NI 43-101, SEC rules and SAMREC compared

JORC is one of a family of codes built on the same international reporting template, published by CRIRSCO in 2006 and last updated in November 2019. The international committee that maintains the template, CRIRSCO, lists national bodies in 16 countries or regions, including Australasia (JORC), Canada (CIM), Europe (PERC), South Africa (SAMREC) and the USA (SME), and says the listed capital of mining companies on their exchanges is more than 80% of the industry total (CRIRSCO, About us). JORC itself is the Australasian code. Other countries run their own CRIRSCO-aligned codes.

Sources: NI 43-101 as published by the Ontario Securities Commission and A&O Shearman’s summary of the SEC mining rules. The categories map closely across codes, but the definitions are not word-for-word the same, so a resource reported under one code is not automatically accepted under another. Check the current version of each instrument with the regulator before relying on a comparison.

What does JORC compliant really mean?

The Code itself warns about the phrase. It says “JORC compliant” refers to the manner of reporting, not to the estimates, and that using it to describe resources is potentially misleading. The words should be read as: reported in accordance with the Code and estimated, or based on documentation prepared, by a Competent Person as the Code defines one (JORC Code, 2012 Edition, clause 6 guidelines). A compliant report is a disclosure standard. It is not a guarantee of grade, mineability or profit.

Four rules are worth knowing when you read company news:

• Exploration Targets are ranges. A target must give a range of tonnes and a range of grade, explain the work done so far, and carry a warning in the same paragraph that the figures are conceptual. It must not be a headline statement.
• A scoping study is not a reserve. It is an order-of-magnitude study and must not be the basis for an ore reserve. If it leans on Inferred resources or an Exploration Target, the report must say how much and in what order.
• Pre-feasibility and feasibility studies are what turn resources into reserves. The Code defines the three study levels in clauses 38 to 40.
• A production target cannot rest only on an Exploration Target, or only on Inferred resources plus an Exploration Target. That is ASX Listing Rule 5.15(a).

Table 1 of the Code is a checklist of five sections: sampling techniques and data, reporting of exploration results, estimation of mineral resources, estimation of ore reserves, and diamonds and gemstones. For significant projects, the relevant sections must be answered on an “if not, why not” basis, normally in an appendix, when results, resources or reserves are reported for the first time or change materially. A blank answer is therefore a flag to ask a question.

Is the JORC Code changing?

Yes, but not yet in force. JORC released a draft revision on 1 August 2024 and received about 8,200 comments by the close of consultation on 31 October 2024 (JORC Code update page). At its 20 August 2026 webinar the committee set a target of finalising the Code, Table 1 and guidance notes in the third and fourth quarters of 2026. The ASX and ASIC then review it, ASX consults on listing-rule changes, and a transition period follows, with timing still to be set (JORC webinar slides, 20 August 2026). Until a new edition takes effect, the 2012 edition remains the one to use.

The slides describe these changes in the draft:

• a three-layer structure: mandatory Code clauses, persuasive guidance notes and a library of extended materials;
• Table 1 cut by half and focused on the points that are material most often;
• “Defined Specialists” removed and Competent Person accountability clarified;
• a Record of Relevant Experience required for all Competent Persons;
• the term ESG dropped, with Modifying Factors described as environmental, social and regulatory factors;
• “Opportunities and Threats” replaced by “Uncertainty”;
• Exploration Targets added to the classification diagram, and a reconciliation clause.

These are proposals as at 20 August 2026 and can change before approval, so check jorc.org before you plan a report around them.

Where satellite screening fits before a JORC resource

A JORC resource needs samples. Typically that means drill holes, trenches or channel samples, analysed in a laboratory, with quality control and a Competent Person’s signature. Satellite data sits earlier in the chain. It can help rank ground before field crews are sent to it, which is where an Exploration Target or the first drilling plan begins. It cannot replace sampling, and a satellite report is not a Mineral Resource or an Ore Reserve.

Farmonaut is a US-based company that applies satellite remote sensing and AI to early-stage mineral exploration, using an area of interest supplied as a KML, KMZ or polygon. It reports cutting early-exploration timelines from months to days and costs by up to 80-85%, delivery in 5 to 20 business days, and work covering more than 100,000 hectares across 20+ minerals and 25+ countries. Its output is an exploration target for sampling, not a JORC public report, and no Competent Person signs it. To see how a screen could apply to your licence, read about satellite-based mineral detection, send details through the mining query form, or contact the team.

▶ Covers three limits of satellite mineral exploration that matter for due diligence. · 2:08

Frequently asked questions

What does JORC stand for?

Joint Ore Reserves Committee. The committee publishes the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves, usually called the JORC Code.

What is JORC in simple words?

It is the rulebook that stops mining companies from overstating what is in the ground. It says which words a company may use (Inferred, Indicated, Measured, Probable, Proved), who must sign the numbers and what supporting detail must be shown.

Is JORC mandatory?

For companies listed on the ASX or NZX, yes, through their listing rules. AusIMM and AIG members are also bound by it. Companies listed elsewhere follow their own country’s rules, such as NI 43-101 in Canada, although many use JORC voluntarily.

What is the difference between a mineral resource and an ore reserve?

A resource is mineralisation with reasonable prospects of eventual economic extraction, graded by geological confidence. A reserve is the part of Measured and Indicated resources shown by a pre-feasibility or feasibility study to be economically mineable, after dilution and losses. In an inclusive statement such as Northern Star’s, reserves are always the smaller number.

Can Inferred resources be turned into reserves?

No. Under the Code an Inferred Mineral Resource must not be converted to an Ore Reserve. It is expected that most Inferred resources could be upgraded to Indicated with more drilling, and only then can they enter reserve work.

Who can be a Competent Person?

A Member or Fellow of AusIMM, AIG or a Recognised Professional Organisation, with at least five years of relevant experience in the style of mineralisation and the activity being signed.

What is JORC Table 1?

A checklist of assessment and reporting criteria in five sections. For significant projects the relevant sections are answered on an “if not, why not” basis when results, resources or reserves are first reported or change materially, so any gap must be explained.

Is a “JORC-compliant” resource guaranteed to be economic?

No. The Code says the phrase describes how the figure was reported, not whether the estimate is right or the ore can be mined at a profit. Resources carry an assumption of reasonable prospects; reserves rest on studies, and both change with price, cost and new drilling.

How does JORC differ from NI 43-101?

Both follow the CRIRSCO template and use similar category names. NI 43-101 applies to Canadian-listed issuers, uses CIM Definition Standards and is built around a filed technical report. JORC applies to ASX and NZX reporting and works through the listing rules and the Competent Person’s signed statement.

Is a satellite report JORC compliant?

No. A satellite screening report gives exploration targets and is not a JORC public report, resource or reserve. It can help decide where sampling and drilling should go, and those results can later support a resource estimate signed by a Competent Person.

Is the JORC Code being replaced?

A revised Code is in preparation. JORC’s August 2026 slides target completion in the third and fourth quarters of 2026, followed by ASX consultation and a transition period. The 2012 edition stays in force until then.