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When drill depths say more than headlines
Press releases from junior gold explorers routinely celebrate “wide mineralization intervals” and “high-grade inclusions.” Investors encountering numbers like “213 meters at 1.24 g/t Au, including 21 meters at 5.77 g/t” for the first time are right to ask what this actually means. The answer rarely comes from a single drill hole. It comes from the geological continuity of a deposit and how well that deposit is positioned for a pre-feasibility study (PFS).
In North America, particularly in jurisdictions such as Alaska or British Columbia, a number of undeveloped gold resources are moving into their next project phase after years of exploration. The gap between a completed mineral resource estimate (MRE) and a PFS is where things get interesting for small-cap investors: this is where it becomes clear whether a project can become economical or whether the geology simply doesn’t hold up.
Resource continuity and what it means for capital
Many investors gravitate toward peak values. A single intercept at 32 g/t sounds spectacular. But the geologists and bankers who actually fund PFS studies are focused on something else: continuity. Is the gold distributed across a large, predictable tonnage, or does it sit in isolated, irregular zones that resist clean modeling?
Intercepts longer than 200 meters suggest the mineralization isn’t pinching out or breaking apart laterally. That simplifies 3D modeling, cuts the cost of a PFS, and makes its conclusions more defensible. For mine financiers, reliable tonnage generally outweighs a single spectacular intersection.
Capping grades: a variable that often goes unexamined
The capping grade, sometimes called the top cut, is the maximum value a single sample point may contribute to a resource calculation, regardless of what the lab actually measured.
The reason for the cap is straightforward. Gold is a “nuggety” metal, meaning its distribution within rock can be wildly uneven. One physical nugget in a drill core sample can drag the average of an entire zone far above what the rest of the material justifies, producing a resource estimate that looks good on paper but doesn’t survive closer scrutiny. Capping limits that effect.
A resource model without defined capping conventions can look very optimistic at the MRE stage and then disappoint when a PFS brings finer-grained data to bear. Projects that document their capping approach clearly in the MRE are signaling a more rigorous attitude toward geological uncertainty — and project financiers notice.
| Metric | What it measures | Why it matters for a PFS |
|---|---|---|
| Interval length | Drill length of the mineralized zone | Indicator of continuity and modelability |
| True width | Actual thickness of the ore zone | Basis for tonnage estimation and mine planning |
| Capping grade (top cut) | Maximum individual sample value in the resource | Protects against distortion by outliers |
| Resource category | Inferred / Indicated / Measured | Determines which portions enter PFS economic scenarios |
From resource to PFS: what changes between phases
A Mineral Resource Estimate under the NI 43-101 standard, which applies in Canada and to Canadian-listed companies, divides resources into three categories: Inferred, Indicated, and Measured. These are not synonyms for reserves. They describe how much geological confidence sits behind a given estimate of mineral quantity.
PFS economic scenarios are built on Indicated and Measured resources. Inferred material, which has the thinnest supporting data, is generally left out. This is why drilling campaigns before a PFS tend to be tightly targeted: the goal is to convert Inferred tonnage into better-supported categories that can actually feed into the study’s numbers.
Drill results in this phase are worth reading as components of a financing argument, not just as geological news. A project that consistently returns wide, classifiable intercepts across successive campaigns is assembling the data foundation a reliable PFS requires. Without it, the study either cannot be completed or produces conclusions no debt provider will touch.
Reading the phase for what it is
The stretch between an MRE and a PFS carries both opportunity and risk, sometimes hard to tell apart within the same project. Investors who work through technical reports and can read drill results will spot earlier whether a project is consolidating its resource base or whether inconsistencies are starting to surface. Even so, the risk stays substantial. A PFS can conclude that a project simply doesn’t work at prevailing metal prices, and that outcome is more common than the accompanying press release tends to suggest.
It pays to check whether new drill holes are positioned in areas that directly strengthen the existing resource model, and whether the share of Indicated-category material is growing relative to Inferred. How a company handles capping grades and true width disclosures often tells you more than the headline numbers in a news release.
Projects in stable North American mining jurisdictions with well-documented geology tend to attract institutional capital more readily than comparable projects elsewhere — not because geography is a proxy for geology, but because lenders price political risk and it shows up in who turns up to a PFS financing round.
Key terms for drilling programs and PFS preparation
- PFS (Pre-Feasibility Study)
- A technical and economic study that evaluates, on the basis of Indicated and Measured Resources, whether a project could be operated profitably under defined assumptions. It is not a guarantee of economic viability, but a study that forms the basis for financing decisions.
- Mineral Resource Estimate (MRE)
- An estimate of the mineral quantity present in the ground under NI 43-101 or JORC standards, subdivided into Inferred, Indicated, and Measured categories. It must be clearly distinguished from Mineral Reserves (Proven/Probable), which require an economic planning basis.
- Capping grade (top cut)
- The maximum value a single sample may contribute to a resource calculation. It protects the resource model from statistical distortion by high-grade outliers, a particular concern for nuggety metals such as gold.
- Resource continuity
- The degree to which mineralization is distributed evenly and without interruption across a deposit. High continuity simplifies geological modeling and increases the reliability of resource estimates.
- True width
- The thickness measured perpendicular to the ore zone, as opposed to the interval length measured along the drill hole, which can appear larger depending on the drill angle. Only true width enables realistic tonnage estimates.
- Inferred resource
- The least well-supported resource category under NI 43-101. It is based on limited data and may only be used in economic studies under restricted conditions.
- Indicated resource
- A resource category with sufficient data density to allow a reliable estimate of tonnage and grade. It is the minimum foundation that can be used for PFS economic calculations.
⚠️ Important notice: This article is for informational and educational purposes only. It does not constitute investment advice, a recommendation, or a solicitation to buy or sell any security. Investments in small-cap exploration and mining companies carry a high risk, including the potential total loss of capital. Before making any investment decision, consult a registered financial advisor and conduct your own analysis. Boersen Post Team is not responsible for decisions taken based on the content published here.
