Gold$2,345.67/oz+0.82%
Silver$29.42/oz-0.34%
Copper$4.12/lb+1.15%
Uranium$85.50/lb+2.41%
Lithium (SC6)$1,240/t-1.08%
TSX-V$1,024.3+0.56%
Gold$2,345.67/oz+0.82%
Silver$29.42/oz-0.34%
Copper$4.12/lb+1.15%
Uranium$85.50/lb+2.41%
Lithium (SC6)$1,240/t-1.08%
TSX-V$1,024.3+0.56%
The Mining Watchlist

How to Read Drill Results

What a Drill Hole Really Tells You

Decoding intercepts, grades and widths in a company's news release.

Key Takeaways
  • A drill result describes a sample through the ground — it is not a resource estimate or proof of a mine.
  • Read grade, interval length, depth and location together. The biggest number rarely tells the whole story.
  • A reported drill interval may be longer than the deposit’s true thickness.
  • Check whether a headline interval includes a much smaller, higher-grade section.
  • The useful question is whether the result strengthens the picture of a continuous, potentially mineable deposit.

Start With the Sentence

A company announces “20 metres at 2 grams per tonne gold from 100 metres.” That means the sampled interval starts 100 metres down the drill hole, extends for 20 metres, and has a reported average gold grade of 2 grams per tonne. It does not mean the company has found a deposit that is 20 metres thick everywhere.

Think of drilling as pushing a thin straw through a layered cake. The straw tells you what it passed through. You still need more samples to understand the shape and size of the whole cake.

The Four Numbers to Read Together

Grade
how much metal the sample contains. Gold and silver are often reported in grams per tonne, written g/t. Copper is often reported as a percentage.
Length
how much of the drill hole the result covers. A long interval can matter, but only in the context of the geology and grade.
Depth
where the interval starts along the hole. This is not necessarily its vertical depth below the surface.
Location
where the hole sits relative to earlier drilling. A result inside a known deposit answers a different question from a result far beyond it.

Drill Length Is Not Always True Width

A hole that cuts across a mineralized zone at an angle can travel through more mineralization than the zone’s actual thickness. Look for the company’s statement about true width, or its explanation that true width is not yet known. The BCSC’s mining disclosure guidance explains why this context matters.

Watch the Word “Including”

In this hypothetical result, “20 metres at 2 g/t, including 2 metres at 15 g/t,” the higher-grade 2 metres is already inside the 20-metre interval.

It is not extra metal to add on top.

Using simple length-weighted arithmetic, the remaining 18 metres averages about 0.56 g/t: [(20 × 2) − (2 × 15)] ÷ 18. This illustration ignores rounding and sampling details, but shows how a narrow rich interval can lift the overall average. Read both numbers.

Look Beyond One Impressive Hole

Compare nearby holes, maps and cross-sections. Are results repeating across an area, or is the headline based on one isolated intercept? Check sampling methods, laboratory testing and quality-control information. A photo of visible mineralization is not a substitute for an assay.

Before drawing a conclusion, write down what changed: more evidence of continuity, a possible extension, better geological confidence, or simply another data point. The next drilling program should help test that interpretation.

Open Pit vs. Underground Mining

Next in the Mining 101 Series

Grade, Tonnage & Scale

Why a little metal over a lot of rock can still add up to a real mine.

Continue →