A drill press release lists intervals: from what depth to what depth, at what grade. Multiplying grade by length gives a single number (gram-metres for gold and silver, percent-metres for base metals) that lets you compare a short high-grade hit with a long low-grade one.
| Hole | From (m) | To (m) | Grade | True width % (optional) |
|---|---|---|---|---|
| Hole | Core length | Est. true width | Grade | gram-metres (true width) | Comparison |
|---|
How to read the result
Worked example
Hole A: 2.5 metres of core at 18.4 g/t gold is 46 gram-metres, or about 32 on an estimated 70% true width. Hole B: 62 metres at 1.1 g/t is 68.2 gram-metres, about 58 on true width. The headline "18.4 g/t" sounds better, but Hole B contains more metal. Whether either is economic depends on the mining method, depth and continuity.
Gram-metres are a comparison tool, not a valuation. A single hole says little about tonnage. What matters is whether many holes, drilled at sensible spacing, keep hitting similar widths and grades. That is how a mineral resource gets defined under NI 43-101.
Watch the "including"
Press releases often highlight a short, very high-grade piece "including" within a longer interval. Don't add the two together; the high-grade piece is already part of the longer interval. Read more in drill results explained.
Common questions
What is a good gram-metre number?
There is no universal threshold. Context matters: an open-pit bulk-tonnage gold deposit can work at grades below 1 g/t over long widths, while an underground vein needs much higher grades. Compare holes within the same project and against similar deposits.
Where does true width come from?
Companies sometimes report an estimated true width as a percentage of core length, or say true width is unknown. If they say it is unknown, treat the core length as an upper bound on the real thickness.
Sources
Educational content only, not investment, tax or legal advice. The Stateside Report does not recommend buying or selling any security. Tax rules depend on your situation; confirm with a qualified tax professional. Full disclosures.