The anatomy of a drill result
A drill result on a press release usually reads something like this:
Hole NQ-26-184 intersected 24.8 metres grading 3.42 g/t Au from 142.5 m depth, including 4.2 m at 12.6 g/t Au from 156.1 m. True width is estimated at approximately 85% of down-hole length.
That single sentence contains all six pieces of information you need:
- Hole ID (NQ-26-184) — lets you cross-reference with project maps and prior releases. The format is usually a project code + year + hole number.
- Width (24.8 m) — how thick the mineralised intercept is, measured along the drill core.
- Grade (3.42 g/t Au) — average concentration of gold across that width.
- Depth (from 142.5 m) — where the intercept starts down the hole. Tells you whether the mineralization is shallow (favourable for open-pit) or deep (underground only).
- Internal high-grade (4.2 m at 12.6 g/t) — a higher-grade section within the broader intercept. Companies often highlight these because they look impressive.
- True width estimate (~85% of down-hole length) — the geometric correction discussed in detail below. The fact that this release discloses it explicitly is a good sign.
Grade units explained
Mining uses several grade units depending on the metal and the concentration involved. Knowing how they relate matters because press releases sometimes switch units within a single document.
| Unit | Means | Typical for | Conversion |
|---|---|---|---|
| g/t | grams per tonne | Au, Ag, Pt, Pd | 1 g/t = 1 ppm |
| ppm | parts per million | Same as g/t, used for trace elements | 1 ppm = 1 g/t |
| % | percent by weight | Cu, Zn, Pb, Ni, Li (as Li₂O), Fe | 1% = 10,000 g/t = 10,000 ppm |
| oz/t | troy ounces per short ton | Au (US-style; less common in modern releases) | 1 oz/t ≈ 34.3 g/t |
| ppb | parts per billion | Au (very early-stage sampling, soil geochem) | 1,000 ppb = 1 g/t |
| TREO | total rare earth oxide % | Rare earths (REE) | Reported as % of contained oxides |
Two unit-related traps to watch:
- Surface samples in ppb. An early-stage explorer reporting "rock chip sample graded 800 ppb gold" is reporting 0.8 g/t — well below any economic threshold. Some press releases lean on ppb because the number looks bigger.
- Lithium reported as Li, Li₂O, or LCE. Lithium can be reported as elemental Li, as the oxide Li₂O, or as lithium carbonate equivalent (LCE). The same deposit produces three very different headline numbers. 1% Li₂O is approximately 0.47% Li, and approximately 2.47% LCE. Compare apples to apples.
Grade tiers by metal — what counts as "high grade"
Grade thresholds are deposit-type and method dependent. The tiers below are rules of thumb for typical deposits at current metal prices — useful for first-pass assessment of a press release. For a deeper-dive on gold grade specifically — including unit conversions, historical context, and why a 30 g/t deposit can be worth less than a 1 g/t deposit — see Gold Grade Explained.
Gold (g/t Au)
| Tier | Open-pit | Underground |
|---|---|---|
| Sub-economic | < 0.5 | < 2 |
| Marginal | 0.5 – 0.8 | 2 – 3 |
| Economic | 0.8 – 1.5 | 3 – 5 |
| Good | 1.5 – 3 | 5 – 10 |
| High grade | 3 – 10 | 10 – 30 |
| Bonanza | 10+ (rare in bulk) | 30+ |
Other metals (rough rules of thumb)
- Silver (g/t Ag). Economic floor ~40 g/t open-pit, ~150 g/t underground. High grade ~300+. Bonanza ~1,000+. The historical Comstock and Cerro Rico mines averaged thousands of g/t.
- Copper (% Cu). Porphyry open-pit economic at ~0.4%, good at 0.7%, high grade at 1%+. Underground vein-style operates above ~1.5-2%.
- Zinc + Lead (% Zn+Pb combined). VMS and SedEx deposits typically need 6%+ combined to be economic. High grade is 10%+ combined.
- Nickel (% Ni). Sulphide deposits economic at ~1% open-pit, 1.5%+ underground. Laterites operate at lower grades (~1%) but higher tonnages.
- Lithium. Hard-rock spodumene economic at 1%+ Li₂O. Brine projects economic at ~500 ppm Li. Clay deposits ~1,500 ppm.
- Rare earths (% TREO). Concentration matters less than the magnet REE proportion (Nd, Pr, Tb, Dy). 1% TREO with 25%+ magnet REE is more valuable than 3% TREO dominated by cerium and lanthanum.
True width vs. down-hole width
Drill holes rarely intersect a mineralised body at 90 degrees. Holes are typically angled to maximise core recovery and to hit specific geological targets. The result is that the intercept measured along the core is longer than the actual thickness of the body.
The geometry: if a mineralised vein is vertical and a hole hits it at 60 degrees from horizontal, an intercept measured 30m along the core represents only about 26m of true (vertical) width. As the angle gets steeper or the body more tilted, the gap widens. For typical drill angles and steeply-dipping bodies, true width is often 60-85% of down-hole width.
Why this matters for press releases:
- Down-hole widths inflate the apparent thickness of the deposit. Headline numbers based on down-hole are flattering.
- Honest releases either give true width directly or state the approximate ratio (e.g., "true width is approximately 75% of intercept length").
- Releases that report "intercept widths" without clarifying down-hole vs. true width are leaning on the ambiguity. Default assumption: down-hole.
Quick rule of thumb
If a press release does not disclose true width, mentally apply a 65-75% factor to the headline intercept length before comparing to peer projects. This is rough but better than treating down-hole as gospel.
Grade × width and gram-metres
The most useful single metric for comparing drill intercepts is grade × true width, usually expressed as gram-metres (g·m) for precious metals or metre-percent (m·%) for base metals. It collapses two variables into one that approximates contained metal per metre of drilling — the actual economic quantity.
Compare these three intercepts:
| Intercept | Width (m) | Grade (g/t Au) | Gram-metres |
|---|---|---|---|
| A | 100 | 1.0 | 100 |
| B | 20 | 5.0 | 100 |
| C | 5 | 20.0 | 100 |
All three intercepts have identical gram-metre values. But they describe very different deposits:
- Intercept A looks unimpressive in a press release. 1 g/t over 100m is the signature of a bulk-tonnage open-pit deposit. Boring but bankable.
- Intercept B is the sweet spot for many Canadian gold juniors. Wide enough for some mining method flexibility, grade strong enough to attract investor attention.
- Intercept C is the bonanza press release. Gets the strongest market reaction in the short term — but whether 5m of 20 g/t represents a continuous mineable structure or an isolated bonanza pocket depends on the surrounding drilling. Single-hole bonanza without confirmation is often a head-fake.
Gram-metres also expose press-release tactics. A company that cycles between releasing a high-grade-narrow intercept one quarter and a low-grade-wide intercept the next, both at comparable gram-metres, may not be advancing the deposit at all — just rotating which hole gets featured. Tracking gram-metres over time is far more informative than tracking headlines.
Intercept types: bonanza, zone-confirming, dud
Not every drill intercept matters the same way to the investment thesis. A useful informal taxonomy:
Bonanza / discovery
Very high grade and/or significant width in new ground. Re-rates the entire project.
Examples: first-pass step-out hitting 30+ g/t Au; new vein intercepted outside known envelope.
Zone-confirming
Confirms continuity of known mineralisation at expected grades. Incremental — does not re-rate the project but de-risks it.
Examples: infill at typical project grade; step-out hitting expected envelope.
Dud
Below-expected grade, lost continuity, or geological surprise (e.g., fault offset). Often the most informative result for de-risking.
Examples: step-out missing the expected vein; infill coming in well below modeled grade.
Press releases pre-categorise results for you, but not always honestly. Watch for:
- Negative drilling buried in unrelated releases. Some companies will pad a press release headlined "new joint venture" or "new appointment" with underwhelming drill results in the back paragraphs.
- Months between drill releases. Drill labs take 4-8 weeks, but if results stop coming and drilling has officially completed, the missing results may be intentionally delayed.
- Selective highlighting. A release that headlines "Hole 5 returns 8 g/t over 10m" while burying Holes 1-4 (all sub-1 g/t) is cherry-picking. Check the appendix or SEDAR+ for the full drill table.
Step-out vs infill vs twin holes
The type of drilling determines what kind of catalyst the result represents.
- Step-out — drilled outside the known mineralised envelope to test if the deposit extends. Successful step-outs grow the deposit. Higher risk, higher reward. The most market-moving result type.
- Infill — drilled inside the known envelope between existing holes. The goal is resource category upgrade (Inferred → Indicated). Lower-risk, lower-reward but essential for advancing toward a feasibility study. For why this matters, see Inferred vs Indicated vs Measured Resources.
- Twin holes — drilled adjacent to an existing hole (usually historical) to verify earlier results. Common when a company acquires a project from a previous owner. Twins that match the historical result are confirmatory; twins that miss are concerning.
- Scout / wildcat — greenfield drilling into geophysical or geochemical targets with no prior drilling. Either makes a discovery or proves the target is empty. Very high variance.
- Definition drilling — extremely tight-spaced drilling (often 5-15m grids) ahead of mining, to precisely define ore boundaries. Usually only done at near-production or operating mines.
Most quality press releases identify program type explicitly. If a release simply says "the company drilled X holes, including the following intercepts" without clarifying whether it was infill, step-out, or scout drilling, that ambiguity is itself informative — usually because the program mixed types and the company is averaging across them.
Geology terms a non-geologist needs
Press releases routinely sprinkle in geological terminology that can intimidate non-specialist investors. A working vocabulary covers the 90% of cases you will see.
Vein
Tabular body of minerals filling a fracture. Often high-grade but narrow. Most historical gold mines exploit vein systems.
Stockwork
A network of small interconnected veins. Larger total volume than a single vein, but with bulk-tonnage style economics.
Disseminated
Mineralisation spread throughout the rock rather than concentrated in veins. Lower grade, but very wide intercepts possible. Porphyry copper is the archetype.
Porphyry
Large-tonnage, low-grade copper or copper-gold deposit type. Multi-billion-tonne porphyries underpin major copper mines globally.
Epithermal
Gold and silver deposits formed near surface by hot fluids. Classic high-grade vein style. Most Latin American and Pacific Rim gold districts are epithermal.
Orogenic
Gold deposits associated with deeply-formed structures during mountain building. The Abitibi gold belt in Canada is the textbook orogenic gold district.
VMS
Volcanogenic Massive Sulphide — base metal (zinc, lead, copper, silver) deposits formed by submarine hydrothermal activity. Often polymetallic.
SedEx
Sediment-hosted exhalative deposits. Large stratabound zinc-lead-silver deposits. Red Dog and Broken Hill are famous examples.
IOCG
Iron Oxide-Copper-Gold. A large, often polymetallic deposit type. Olympic Dam in Australia is the archetype.
Skarn
Mineralisation formed where intrusive rocks contact carbonate (limestone) host rocks. Can host gold, copper, tungsten, iron.
Alteration
Chemical changes in rock around mineralisation. Specific alteration types (silicification, sericite, propylitic, potassic) are diagnostic of deposit type and proximity.
Strike
Compass direction of a mineralised body at the surface. "Strike length" is how far the body extends along that direction.
Dip
Angle a mineralised body makes with horizontal. A vertical vein has a 90° dip; a horizontal layer has a 0° dip.
Pinch and swell
Mineralised body that thickens and thins along strike. Common in shear-zone gold and can complicate resource estimation.
Cut-off grade
Minimum grade at which rock is counted as ore. Lower cut-offs increase tonnes but reduce average grade. See the NI 43-101 guide for how this affects resource numbers.
Recovery
Percentage of metal that can be extracted from ore during processing. Free-milling gold can hit 95%+; refractory ore may drop to 70-80%.
For deeper definitions of these and related terms, see the Mining Glossary.
The press-release tricks to watch for
None of these is fraud — they are all technically compliant disclosure. They are techniques used by IR teams to present ordinary results favourably. Spotting them is most of what separates informed retail investors from the rest.
1. Composite intervals with internal dilution
A headline like '50m at 2 g/t Au' may be composed of 10m at 8 g/t plus 40m at 0.5 g/t. The composite average is technically correct but masks a narrow high-grade vein in mostly-waste rock. Always look for an internal breakdown or a 'including' sub-interval that tells you where the grade actually sits.
2. Down-hole width without true width
If a release reports widths without specifying true width, default to assuming down-hole. For steeply-dipping bodies drilled at typical angles, real-world thickness is often 60-80% of the reported number.
3. Cherry-picked holes
A press release titled 'positive drill results' that only details 2-3 of 10 holes drilled is selecting the best. Other holes from the same program either hit lower grades or missed. Check the SEDAR+ filing or the drill location map for the complete picture.
4. Aggressive gold-equivalent calculations
Poly-metallic deposits use gold-equivalent (AuEq) to combine multiple metals into one headline grade. AuEq depends on assumed metal prices and recoveries. A 3 g/t AuEq calculated at $2,400 gold and $35 silver looks worse at $2,100 gold and $27 silver. Always check the assumptions footnote.
5. ppb instead of g/t
An early-stage company reporting '600 ppb gold from a surface sample' is reporting 0.6 g/t — below most economic thresholds. ppb in soil or rock chip work is normal and useful for vectoring, but ppb-based hype in a stock-promotion context is a red flag.
6. Inverted depth-to-target language
Phrases like 'mineralisation extends to depth' or 'open in all directions' sound positive but can be filler when no actual new intercepts have been added. If a release uses this language without specific new step-out hits, the company is signalling activity without progress.
7. Historical data dressed as new news
Some releases describe previously-published intercepts or historical drilling from prior operators as if they were new. Read carefully — anything described as 'previously reported,' 'historical,' or 'from prior operator' is old news.
8. Visual estimates ahead of assays
Pre-assay visual estimates ('visible gold logged') can move stocks but are not confirmed grades. Geologists can see gold flecks in core but cannot tell concentration without an assay. Some visible-gold intercepts assay below 1 g/t; others come in at 100+. Wait for assays.
9. Promotional headline grades from short intervals
A 0.5m intercept at 40 g/t is technically a high-grade hit but contributes 20 gram-metres — less than a 50m intercept at 1 g/t. Short-interval bonanza headlines should be read in gram-metre terms before assigning weight.
10. Delayed disclosure of disappointing programs
A successful program produces a string of release dates. A drill program that completed two months ago with no further releases is statistically more likely to have produced disappointing results than expected. The absence of news is its own news.
Worked example — translating a real drill table
Here is the kind of drill table you will see in the body of a press release. The headline read "multiple high-grade intercepts including 24.0m at 3.85 g/t Au."
| Hole | From (m) | To (m) | Width (m) | Au (g/t) | g·m |
|---|---|---|---|---|---|
| AB-26-01 | 128.4 | 152.4 | 24.0 | 3.85 | 92.4 |
| incl. | 141.0 | 145.5 | 4.5 | 18.2 | 81.9 |
| AB-26-02 | 85.0 | 102.0 | 17.0 | 1.42 | 24.1 |
| AB-26-03 | 210.5 | 214.0 | 3.5 | 12.4 | 43.4 |
All widths down-hole. True width estimated to be 70-80% of intercept length. Composite grades weighted by interval.
Translation, hole by hole:
- AB-26-01 headline (24m at 3.85 g/t = 92.4 g·m) is a strong intercept by any measure. But check the included 4.5m at 18.2 g/t — it accounts for 81.9 g·m out of the 92.4 total. That means the other 19.5m of the intercept averages about 0.54 g/t — below the open-pit economic floor. The "24m at 3.85 g/t" is technically correct but mostly represents a narrow high-grade vein within a much wider zone of waste rock. The deposit needs underground mining at the 4.5m vein, not bulk open-pit at the 24m envelope.
- AB-26-02 (17m at 1.42 g/t = 24.1 g·m) is a moderate result. Reasonable open-pit grade over usable width. Not a discovery, but a useful zone-confirming intercept if it is within the modeled envelope. About a quarter of the value of AB-26-01 on a gram-metre basis.
- AB-26-03 (3.5m at 12.4 g/t = 43.4 g·m) is half of AB-26-01's value but with no internal dilution. It is high-grade and clean. The narrower width limits mining method options but the grade is excellent.
- True width. Applying the disclosed 70-80% factor: AB-26-01's 24m becomes about 18m true width. The 4.5m internal high-grade becomes about 3.4m. Still meaningful, but the down-hole headline is rosier than reality.
The headline reading the release as "24m at 3.85 g/t Au" is technically accurate but conceals that the deposit shape on display is a narrow high-grade vein with sub-economic wallrock — a meaningfully different mining proposition than what the headline implies. This is normal disclosure, not fraud. It is also why reading the body of the release matters more than the title.
Tools to speed this up
Tracking drill results manually across the 500+ companies in the junior mining universe is impractical. The tools below automate the work:
Drill Scanner →
Scans recent drill press releases across the database. Filter by grade-times-width, by metal, and by company. Finds the real catalysts under the noise.
Grade Ranker →
Compare resource grades across 500+ companies. Filter for deposits in your preferred grade tier — sub-economic surprises don't make the list.
NI 43-101 Analyzer →
AI-assisted extraction of resource tables and economic summaries from any uploaded technical report.
Company Database →
Browse 500+ junior miners. Each company page lists recent news releases including drill announcements.
Frequently Asked Questions
How do you read a mining drill result?
Every drill result has three numbers that matter: depth (where the intercept starts and ends down the hole), width (how thick the mineralised zone is), and grade (concentration of the target metal). The most important derived number is grade-times-width — a 1.0 g/t intercept over 100m and a 10 g/t intercept over 10m both produce a 'gram-metre' value of 100, but they may represent very different deposits. Always check the true width (perpendicular to the mineralised body) vs. the down-hole width, the cut-off grade applied, and whether the interval is a single high-grade hit or a composite of many intervals stitched together.
What does g/t mean in mining?
g/t means grams per tonne. It is the standard concentration unit for precious metals in mining (gold, silver, platinum group metals). One g/t means one gram of metal in one tonne of rock — equivalent to one part per million. For gold, anything above 1 g/t is considered economic for open-pit mining at current prices, 3-5 g/t is good for underground, and 10+ g/t is high grade. Bonanza grade is loosely anything above 30 g/t. Base metals like copper and zinc are reported in percent (%) instead, since their concentrations are typically 100-1,000 times higher than precious metals.
What is a bonanza grade in gold mining?
Bonanza grade is an informal term for exceptionally high gold concentrations, generally above 30 g/t and often used for grades above 100 g/t. The term originates from the historical California and Comstock Lode mines where rare 'bonanza' veins produced astronomical grades. Modern bonanza intercepts get heavy press coverage because they signal high-grade structures that can be mined profitably even at low tonnages. However, bonanza intercepts are often narrow and erratic — they may not represent a continuous mineable zone, and a single 200 g/t hole does not guarantee a deposit.
What is the difference between true width and down-hole width?
Down-hole width is the length of the mineralised intercept measured along the drill core. True width is the actual thickness of the mineralised body measured perpendicular to its strike and dip. They are only equal when the drill hole intersects the mineralised body at a perfect 90-degree angle. In practice, holes are usually angled — so a 30m down-hole intercept might represent only 15-20m of true width. Honest press releases either disclose true width explicitly or say 'true width is estimated to be approximately X% of the down-hole length.' Marketing-first releases highlight down-hole widths and bury or omit true widths.
What is grade times width and why does it matter?
Grade times width (often called gram-metres or g·m) is the simplest way to compare drill intercepts across different widths and grades. A 5 g/t intercept over 20m gives 100 g·m, identical to a 1 g/t intercept over 100m. The metric strips out the cosmetic appeal of high-grade-narrow vs. low-grade-wide and lets you compare the actual contained metal per metre drilled. Most serious investors and geologists track gram-metres rather than headline grades. A drill program where average gram-metres are increasing over time signals an improving deposit; one where they are decreasing is the opposite — even if individual headline holes look impressive.
What is gold-equivalent (AuEq) grade?
Gold-equivalent (AuEq) is a calculated grade that converts the value of other metals in the rock (silver, copper, etc.) into the equivalent quantity of gold at assumed metal prices and recovery rates. It is used for poly-metallic deposits where multiple metals contribute to revenue. The catch: AuEq depends entirely on the assumed prices and recoveries. A press release reporting '2.5 g/t AuEq' may use $2,400/oz gold and $30/oz silver — if prices fall, AuEq falls. Always check the assumptions used in the AuEq calculation, and compare them to current spot prices. AuEq is most honest when the calculation method and assumptions are disclosed prominently.
What is the difference between step-out drilling and infill drilling?
Step-out drilling tests new ground outside the known deposit boundary — it is exploration aimed at growing the deposit. A successful step-out hole extends the mineralisation laterally or to depth and signals the deposit may be larger than previously thought. Infill drilling fills gaps between existing holes inside the known deposit — its purpose is to upgrade resource categories (Inferred to Indicated, Indicated to Measured) rather than to add new tonnes. Step-outs are higher-risk, higher-reward catalysts; infill is methodical resource confirmation. The drill program type tells you what kind of news you are reading.
What is a composite interval in a drill result?
A composite (or weighted average) interval is a single grade-width figure calculated by averaging multiple smaller intercepts within a longer down-hole range. Companies use composites to report 'overall' results, but the technique can blend high-grade and low-grade sections to make average grades look better than any continuous mineralised zone actually is. The red flag is internal dilution — a composite of '50m at 2 g/t' that breaks into '10m at 8 g/t, 30m at 0.3 g/t, 10m at 2 g/t' is not the same as 50 continuous metres at 2 g/t. Honest press releases disclose the internal breakdown beneath the composite headline. If a release reports composites only, dig into the appendix or the SEDAR+ filing for the raw intervals.
How long does it take to get drill results?
Typically 4-8 weeks from drilling to released results, though it can stretch to 3+ months during peak season when commercial assay labs are backlogged. The workflow is: drill the hole, log the core, cut and sample, ship to lab, lab does sample prep, lab assays, results come back, company reviews and (for material results) issues a press release. The delay is mostly the assay lab — independent labs like ALS, SGS, and Bureau Veritas process tens of thousands of samples per week and queue depth varies. Companies sometimes pre-release visual observations from the core ahead of assays — these can move stocks but are not yet confirmed.