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How to read drill results

Drill results are the main news a junior miner puts out. Each line packs a hole, a length, a grade and a depth into a few characters. Here is how to unpack one, and what else the release should tell you.

One line, taken apart

A typical headline result reads like this:

PTD-014: 12 m at 2.4 g/t Au from 85 m, including 3 m at 7.1 g/t Au from 89 m

PTD-014 is the hole's name. Prefixes often tell you the drilling method (DD for diamond core, RC for reverse circulation) or the prospect.
12 m is the length of the mineralised interval, measured along the hole.
2.4 g/t Au is the average grade over that length: 2.4 grams of gold per tonne of rock. Base metals such as copper and zinc are given in per cent, lithium usually as % Li₂O, rare earths in ppm TREO. See grams per tonne and other grade units.
from 85 m is where the interval starts, again measured down the hole from the collar (the point where the hole enters the ground).
including 3 m at 7.1 g/t is a richer part inside the 12 m. It is not extra metal on top.

Hover or tap a part of the result to find it on the section. The scale is the same all the way down the hole. Schematic: the hole and the numbers are made up.

The example above is made up to show the format. The latest drill results on the homepage link real releases, each opened on its 3D model.

Downhole width and true width

Most holes are drilled at an angle, and most mineralised zones dip. The interval length is the stretch of hole inside the zone, which is only the zone's real thickness when the hole crosses it at right angles. A hole that cuts a zone at a shallow angle can report a long interval through a thin zone.

Drag the angle between the hole and the vein. The interval length stays the same; the true width the zone really has changes with the angle (true width = interval × sin of the angle).

A good release says whether widths are downhole or estimated true widths, and gives the hole's angle (dip) and direction (azimuth) so you can see the geometry. Seeing the holes in 3D makes this much easier: you can see which way each hole was drilled and how the intervals line up.

Grade, cut-offs and how intervals are built

Laboratories assay the hole in samples, typically 1 to 2 m long. The company then combines consecutive samples into reported intervals using rules it should state, for example: samples above 0.5 g/t gold, allowing up to 2 m of lower-grade material inside an interval. Change the rules and the same hole gives different headlines, so look for them in the notes or the JORC Table 1.

Cut-off grade: the lowest grade counted in an interval.
Internal dilution: how much below-cut-off rock an interval may contain.
Top cut: a cap on very high single assays so one nugget does not lift the whole average. Releases should say whether a top cut was applied.
Metal equivalents (AuEq, CuEq): several metals rolled into one figure. They depend on the prices and recoveries assumed, which the release must state.

Grade times length gives gram-metres (or per cent-metres): 12 m at 2.4 g/t is 28.8 g·m. It is a quick way to compare intervals, nothing more.

Twenty-two 1 m assays from one made-up hole. Change the rules and watch the headline change. With the defaults (0.5 g/t cut-off, up to 2 m of internal dilution, 5 g/t for the 'including') you get the example on this page.

How the hole was drilled and sampled

Diamond drilling recovers a solid cylinder of rock (drill core) that geologists can log and cut in half for assay. Reverse circulation (RC) drilling returns rock chips, faster and cheaper but with less detail. Aircore and RAB are shallow, early-stage methods. The release should name the method, the sample length, the laboratory and the assay method (for gold usually fire assay; for base metals and lithium usually an acid digest or a fusion with ICP finish).

Two drillers in hard hats beside a diamond drilling machine inside a drill shed, 1962 — Ore exploration drilling at Pyhäjärvi, Finland, 1962: deep-hole driller Erkki Kaartinen (left) and his assistant Urho Leskelä at the drill. Photo: Finnish Heritage Agency (Museovirasto), Finna, CC BY 4.0.

Quality control means standards (samples of known grade), blanks and duplicates inserted with the real samples. Companies reporting under the JORC Code describe all of this in Table 1; under NI 43-101 a Qualified Person verifies the data.

Where the hole sits

A result means most next to the holes around it. Is it an infill hole inside a known zone, a step-out that extends it, or a first hole into a new target? The collar table (easting, northing, elevation, azimuth, dip and depth for each hole) and a plan or section let you place it. Results from the same zone that repeat from hole to hole build the confidence that a resource estimate later needs.

A checklist for any drilling release

Are all holes reported, including the ones with no significant results?
Is there a collar table with coordinates, dip, azimuth and depth?
Are widths downhole or true, and is that stated?
Are the cut-off, internal dilution and any top cut stated?
Are these laboratory assays, or visual estimates or handheld XRF readings awaiting assays?
Are metal equivalents explained, with the prices and recoveries used?
Is there a Competent Person (JORC) or Qualified Person (NI 43-101) statement?

Tick off a release as you read it. Nothing is saved or sent.

Try it on a real release. The investor flight simulator takes WA1 Resources' Luni drill results of 19 October 2026 from the headline down to the intervals in 3D: one line decoded, the full intercept around it, true width and the grade slider.

Questions

What does "12 m at 2.4 g/t from 85 m" mean?

The hole passed through 12 metres of rock that averaged 2.4 grams of the metal per tonne, starting 85 metres down the hole from where it was collared at the surface. All three figures are measured along the hole, not straight down.

What is the difference between downhole width and true width?

Downhole width is the length of hole that cut the mineralised zone. True width is the thickness of the zone itself, measured at right angles to it. They are the same only when the hole crosses the zone at 90 degrees; at a shallower angle the downhole length is longer than the true width. Releases should say which one they quote.

What does "including" mean in a drill result?

It marks a higher-grade part inside the longer interval. In "12 m at 2.4 g/t including 3 m at 7.1 g/t", the 3 m are part of the 12 m, not extra to them.

What are gram-metres?

Grade multiplied by length: 12 m at 2.4 g/t is 28.8 gram-metres. It lets you compare a short high-grade interval with a long lower-grade one, but it says nothing about whether either could be mined.

What is a good drill result?

There is no single number. It depends on the metal, the deposit style, the depth and how the deposit would be mined, and on whether nearby holes show the same thing. As a rough guide, open pits can work at much lower grades than underground mines, which need higher grades over widths that can be mined. A drill result is one sample of a deposit, not a resource.

Why do some releases have results but no assays?

Some companies report what they see in the core or measure with a handheld XRF before the laboratory assays come back. These visual estimates are not assays. ASX rules require them to carry a clear cautionary statement, and the assays can differ.

Sources

An explainer of how mining companies report their work, written from the public codes and rules linked above. It describes the documents and does not rate any company, project or result. Not investment advice.