Drilling terms, in plain English

A quick reference for reading drill results — no geology degree required.

Intercept (intersection)

A length of drill core or cuttings that returned significant grade, quoted as length @ grade — e.g. “12m @ 3.1 g/t Au”. The headline unit of a drill result.

Grade

How rich the rock is. For gold, measured in g/t (grams per tonne); for base metals usually % (per cent). Higher is better, but width and depth matter too.

g/t

Grams per tonne. 1 g/t gold = one gram of gold in a tonne of rock. Bulk-tonnage mines can work below 1 g/t; “bonanza” hits run into the tens or hundreds.

Cut-off grade

The minimum grade counted as “ore” when compositing intervals. Raise it and only the richer material shows; lower it and more is included. You can adjust this in the viewer.

Collar

The starting point of a drill hole at surface — its coordinates, elevation, direction (azimuth) and angle (dip). Collars are the dots you see on the satellite map.

Downhole / from–to

Positions measured along the drill hole, not vertical depth. “From 40m to 52m” means an interval 40–52 metres along the hole.

Azimuth & dip

The direction a hole is pointed (azimuth, 0–360°) and how steeply it plunges (dip, degrees below horizontal). Together they define the hole's path underground.

RC vs diamond drilling

Two common methods. RC (reverse circulation) is fast and cheap, returning rock chips — good for grade. Diamond drilling recovers solid core, giving geological detail but at higher cost.

Assay

The lab measurement of metal content in a sample. Assays are what turn a length of core into a grade.

Strike & dip (of a body)

The compass direction a mineralised zone runs along (strike) and the angle it tilts into the ground (dip) — how the deposit is oriented in 3D.

JORC

The Australasian code governing how companies report exploration results and mineral resources. A resource is an estimate of contained metal; it is a much higher bar than raw drill intercepts. Aurigrade shows drilling, not resource estimates.

Ounce (oz) / Moz

How gold endowment is quoted. 1 troy ounce ≈ 31.1g. Moz = million ounces — the scale at which resources and reserves are usually discussed.

Dry hole

A hole that returned no significant grade above cut-off. Still useful — it constrains where the mineralisation isn't.

Hit rate

The share of a deposit's holes that returned a significant intercept — a rough gauge of how consistently the drilling is finding mineralisation.