This page was created by Thunder Gold Corp. All statements about mineral resources refer to the January 19, 2026 NI 43-101 mineral resource estimate prepared by Micon International Limited. Mineral resources are not mineral reserves and do not have demonstrated economic viability.
Gold exploration drilling
| Gold exploration drilling is how a company turns a geological idea into a number you can read on a spreadsheet. For Thunder Gold Corp (TSXV: TGOL | OTCQB: TGOLF | FSE: Z25), drilling is the tool that has defined the 3.5 Moz resource at the Tower Mountain gold property, 40 km west of Thunder Bay, Ontario. This page explains how gold exploration drilling works, from the diamond bit to the intercepts that appear in the company’s news releases. |
|---|
Diamond Drilling and How It Works
Most gold exploration in Ontario uses diamond drilling, not the cheaper reverse circulation, or RC, rigs seen in some other jurisdictions. A diamond drill uses a hollow steel bit impregnated with industrial diamonds to cut a cylindrical core, typically NQ or HQ diameter, from the rock. The core is brought to surface in runs, logged by a geologist, marked for sampling and then photographed. The advantage of diamond drilling is that it preserves the structure and texture of the rock, which matters in shear-hosted gold systems where the relationship between mineralisation and host rock controls grade. At Tower Mountain, where gold is disseminated in altered volcanic and intrusive rocks, that structural context helps the geologists understand where the mineralisation is going.
Core Recovery, Logging and Sampling
A drill hole is only as good as the data it produces, and core recovery is the first test. If the core crumbles in a fracture zone, the geologist has a gap in the data at exactly the place that may matter most. Recovery is recorded as a percentage, and intervals with poor recovery are flagged when the resource estimate is built. Once logged, the core is split with a diamond saw: one half goes to the laboratory, the other half is stored in a core shed for reference. View representative core from the Tower Mountain programme.
QA/QC: The System Behind the Numbers
Every assay result that feeds a news release or a resource estimate comes with a QA/QC programme, because a laboratory can produce a wrong number and no system catches it automatically. The standard programme inserts blanks, certified standards and duplicates into the sample stream at regular intervals – typically every 20 samples. A blank that returns gold means contamination; a standard that drifts outside its certified range means the laboratory’s calibration has slipped; a duplicate that disagrees with the original means the sampling was uneven. Thunder Gold’s work at Tower Mountain is underpinned by QA/QC programmes run through accredited laboratories, the same standard expected under NI 43-101. The Qualified Persons who signed the January 19, 2026 Micon International estimate – William Lewis, P.Geo., Charley Murahwi, P.Geo., FAusIMM, and Tudorel Ciuculescu, P.Geo. – reviewed that data as part of the resource work.
From Assay to a Reported Intercept
Assaying for gold is usually done by fire assay with an ICP or gravimetric finish: the sample is fused with flux, the lead button is collected and the gold content measured. Results come back as grams per tonne, g/t, over the sampled interval. A reported intercept is not the raw assay; it is a composite. The company chooses a cut-off grade, typically 0.1-0.5 g/t Au for a bulk-tonnage system, and reports the down-hole length over which the grade averages above that cut-off, allowing narrow higher-grade intervals inside it. A single high assay – 941.0 g/t Au over 1.5 m in hole TM23-137, the highest ever reported at Tower Mountain – is a narrow vein, while a long low-grade interval such as 1.7 g/t Au over 250.4 m in TM23-139 is the bulk system. Both are real; they describe different parts of the same deposit.
Reading the Tower Mountain Drill Results
The 2026 programme of 15,000-25,000 m of infill and expansion drilling has produced a steady flow of intercepts. Representative examples, drawn from company news releases, include:
| Hole / Release | Down-hole interval (m) | Gold grade (g/t Au) | Notes |
|---|---|---|---|
| TM23-137 | 1.5 | 941.0 | Highest grade ever reported at Tower Mountain |
| TM23-139 | 250.4 | 1.7 | Broad, continuous bulk-tonnage interval |
| TM23-140 | 24.5 | 5.3 | Higher-grade zone within the system |
| TM23-143 | 36.3 | 5.9 | Higher-grade zone within the system |
| Oct 26, 2026 release | 336.0 | 0.407 | Continuous mineralisation |
| Oct 26, 2026 release | 290.1 | 0.527 | Second long interval in same release |
| Oct 19, 2026 release | 102.0 | 1.178 | New target area |
Project to date, Tower Mountain has seen 235 drill holes for approximately 47,000 m, and all-in drilling costs run about C$250-275 per metre, among the lowest in Canada. The company’s reported discovery cost of C$3.95 per ounce is a measure of how cheap the drilling has been relative to the ounces found.
Infill Drilling, Step-Out Drilling and the 2026 Programme
Drilling serves two different purposes, and confusing them is one of the most common mistakes in reading results. Infill drilling closes the space between existing holes to increase the confidence of the resource, converting Inferred material to Indicated. Step-out drilling extends the mineralised zone beyond the current resource footprint, which is where new ounces are found. The 2026 programme does both: infill to support a Q4 2026 resource update targeting 1.5 Moz Indicated and 3.5 Moz Inferred, and expansion to test the P-Target on the eastern contact, which returned grades and interval lengths statistically indistinguishable from the 47,000 m western dataset. A 2026 magnetotellurics airborne survey was also awarded to map structure beneath cover.
What a Drill Programme Costs
Cost per metre is one of the few metrics that is genuinely comparable across projects. At Tower Mountain, all-in drilling costs of about C$250-275 per metre compare favourably with many Canadian peers, and the C$3.95 per ounce discovery cost reflects the large metres drilled relative to the ounces added. Investors should treat both numbers as company-reported and check them against the NI 43-101 technical report, filed March 10, 2026, which describes the data underpinning the resource. See the full results list and the technical report.
Frequently Asked Questions
Q: What is gold exploration drilling?
A: Gold exploration drilling is the process of using a diamond-tipped drill to recover cylindrical core from the ground so geologists can sample and assay it. At Tower Mountain, Thunder Gold Corp has completed 235 holes for approximately 47,000 m to define and expand its 3.5 Moz resource.
Q: How does a diamond drill work at Tower Mountain?
A: A diamond drill uses a hollow bit impregnated with industrial diamonds to cut NQ or HQ diameter core from altered volcanic and intrusive rocks. The core is logged, split with a diamond saw and sent to an accredited laboratory for fire assay, all under a QA/QC programme.
Q: What does a drill intercept of 250 metres mean?
A: It is the down-hole length within which the averaged gold grade exceeds a reported cut-off. Because holes are drilled at an angle to the mineralised zone, the true width is usually shorter than the reported intercept length.
Q: How much does gold exploration drilling cost?
A: All-in drilling costs at Tower Mountain are about C$250-275 per metre, among the lowest in Canada, and the company’s reported discovery cost is C$3.95 per ounce. These are company-reported figures that should be verified against the NI 43-101 technical report.
Q: What is the difference between infill and step-out drilling?
A: Infill drilling closes the gap between existing holes to upgrade resource confidence, converting Inferred material to Indicated. Step-out drilling extends the mineralised zone beyond the current footprint, which is where new ounces are discovered. The 2026 Tower Mountain programme does both.
Gold drill intercepts
| A drill intercept is the number you see in every gold exploration news release, and it is easy to misread. At Tower Mountain, Thunder Gold Corp (TSXV: TGOL | OTCQB: TGOLF | FSE: Z25) reports intercepts such as 1.7 g/t Au over 250.4 m, and that single line hides several judgement calls. This section explains how to read a gold drill intercept: down-hole length versus true width, cut-off grades, compositing, and why grades are reported in grams per tonne over metres. |
|---|
Down-Hole Length vs True Width
The first number in an intercept, the metres, is the length of rock the drill passed through, not the width of the gold zone. A hole drilled at 60 degrees to a vertical zone will cross more rock than a hole drilled perpendicular to it, so the down-hole length is almost always longer than the true width of the mineralisation. The true width depends on the angle between the drill direction and the zone, and a competent geologist can estimate it from the geometry. A 250.4 m down-hole interval might correspond to a true width of 100-150 m in a gently dipping system, or far less in a steep one. The responsible approach is to treat the down-hole length as the reported figure and to look for a true-width note in the release or the technical report – and to be sceptical of any intercept that quotes only a very long down-hole length without context.
Cut-Off Grades: What Gets Reported
A cut-off grade is the threshold above which an interval is reported, and it is a choice, not a measurement. In a bulk-tonnage system such as Tower Mountain, cut-offs typically fall between 0.1 and 0.5 g/t Au, because the economic value comes from volume. A higher cut-off produces shorter, higher-grade intercepts that read more dramatically; a lower cut-off produces longer, lower-grade intercepts that are closer to what a mine would actually process. The company’s published intercepts use cut-offs appropriate to each programme, and the Micon International resource estimate uses a 0.19 g/t Au cut-off for the open-pit optimisation. Comparing two intercepts reported at different cut-offs without adjusting for that difference is one of the most common errors in gold exploration.
Compositing and Interval Cutting
Compositing is the process of averaging assays over a reported interval, and it involves choices. The first is the maximum allowable interval: if a single assay runs far above the rest, the geologist may cap it at a defined maximum value so that one rich vein does not dominate the average. The second is the minimum interval: very short runs of high-grade material are often included only if they sit within a longer mineralised interval. The third is the cut-off itself: intervals below the cut-off are excluded, which can make a deposit look discontinuous if the cut-off is set aggressively. None of these choices is dishonest, but they shape the number you read, and the NI 43-101 technical report filed March 10, 2026 should describe the methods used at Tower Mountain.
Why Grades Are Reported in g/t Over Metres
Grams per tonne over metres is the standard unit for a reason: it combines grade and width into a single number that is roughly proportional to the contained metal. A 1 m interval at 10 g/t and a 10 m interval at 1 g/t both contain about 10 grams per tonne-metre, but they are very different geological and economic objects. Grade alone tells you nothing about scale; width alone tells you nothing about concentration. The g/t-over-metres format also makes comparison straightforward once you know the cut-off and the true width, which is why it is used in resource estimates, news releases and technical reports alike.
A Worked Example from Tower Mountain
Consider two real intercepts from the Tower Mountain programme. Hole TM23-139 returned 1.7 g/t Au over 250.4 m down-hole: a long, continuous interval at modest grade, the kind of result that adds tonnes to a resource. Hole TM23-137 returned 941.0 g/t Au over 1.5 m: a very high grade over a very short interval, the kind that makes a news headline but contributes little to a bulk-tonnage resource. Both are genuine. The first tells you the system is large and consistent; the second tells you narrow high-grade veins exist within it. A reader who compared only the headline grade would conclude the deposit was either extremely rich or extremely poor, when the truth is that it is a large, low-grade system with local high-grade zones.
| Hole | Down-hole length (m) | Grade (g/t Au) | What it suggests |
|---|---|---|---|
| TM23-139 | 250.4 | 1.7 | Large, continuous bulk-tonnage mineralisation |
| TM23-137 | 1.5 | 941.0 | Narrow high-grade vein within the system |
| Oct 26, 2026 | 336.0 | 0.407 | Long continuous interval at low cut-off |
| Oct 26, 2026 | 290.1 | 0.527 | Second long interval, modestly higher grade |
How to Compare Two Intercepts Honestly
When comparing two intercepts, check five things before drawing any conclusion: the cut-off grade used; whether the length is down-hole or true width; the maximum interval and capping rules; the hole spacing and orientation; and the geological context, because a step-out hole in new ground and an infill hole in known ground are answering different questions. If a competitor reports a longer intercept at a higher grade, ask whether their cut-off is higher and their zone is steeper before declaring the deposit better. Read the full intercepts to work through the Tower Mountain data yourself.
Why the Headline Grade Can Mislead
The single highest grade in a release is the number that travels furthest on social media and in newsletters, and it is usually the least informative. At Tower Mountain, the 941.0 g/t Au over 1.5 m in TM23-137 is a genuine and remarkable result, but it represents a sliver of rock inside a much larger, lower-grade system. The deposit’s economic character is set by the long intervals – 336.0 m at 0.407 g/t, 290.1 m at 0.527 g/t, 250.4 m at 1.7 g/t – not by the one rich assay. A deposit that makes the news for a 1,000 g/t intercept and then reports nothing else is a different proposition from one that reports consistent wide intervals, and the difference is visible only in the full table, not the headline. Read the full intercepts and check the release against the technical report before judging it.
Frequently Asked Questions
Q: How do you read a gold drill intercept?
A: Read the cut-off grade first, then check whether the length is down-hole or true width, since holes drilled at an angle cross more rock than the zone is wide. Then note the compositing rules and the geological context before comparing it with other results.
Q: What is the difference between down-hole length and true width?
A: Down-hole length is the distance the drill travelled through rock, which is almost always longer than the true width of the mineralised zone. True width is the actual thickness of the gold-bearing rock, calculated from the angle between the hole and the zone.
Q: Why are grades reported in g/t over metres?
A: Grams per tonne over metres combines grade and width into one number that is roughly proportional to contained metal, making deposits comparable. A 1 m interval at 10 g/t and a 10 m interval at 1 g/t contain the same metal but are very different objects.
Q: What is a cut-off grade and why does it matter?
A: A cut-off grade is the threshold above which an interval is reported, and it is a choice, not a measurement. At Tower Mountain the resource estimate uses 0.19 g/t Au, and a higher cut-off produces shorter, higher-grade intercepts.
Q: How do you compare two drill intercepts honestly?
A: Check the cut-off, whether the length is true width, the capping and maximum-interval rules, the hole spacing, and the geological context. An infill hole in known ground and a step-out hole in new ground are answering different questions.
Gold drilling results
| Every gold exploration company publishes drilling results, and the numbers look similar on the surface. In fact, Thunder Gold Corp (TSXV: TGOL | OTCQB: TGOLF | FSE: Z25) released intercepts in 2026 such as 0.407 g/t Au over 336.0 m and 1.178 g/t over 102.0 m at Tower Mountain, and reading them correctly matters more than reading them quickly. This section explains what gold drilling results actually tell investors, and how to compare them honestly. |
|---|
What a Drill Result Actually Tells You
A drill result is a measurement of a single point in a three-dimensional geological problem. It tells you the gold content of the rock between two depths in one hole, at one moment in time, using one laboratory’s methods. It does not tell you the size of the deposit, the grade of the rest of it, or whether it can be mined. What it does tell you is whether the geological theory that predicted mineralisation at that location was correct, and how strong and continuous the mineralisation is. Over many holes, the results build the dataset that becomes a resource estimate – the January 19, 2026 Micon International estimate for Tower Mountain, which reported 34.0 Mt Indicated at 0.46 g/t Au and 211.1 Mt Inferred at 0.45 g/t Au, about 3.5 Moz total. Mineral resources are not mineral reserves, and no economic viability has been demonstrated.
Grade, Width and Continuity
Three properties define every result: grade, width and continuity. Grade is the gold concentration; width is the length of the interval; continuity is whether similar results appear in adjacent holes. A high grade with no continuity is a vein fragment, not a resource. A wide interval with a low grade may be the most valuable result of all, because bulk-tonnage economics depend on tonnes. At Tower Mountain, the 2026 results cluster around wide, low-grade intervals – 411.0 m at 0.514 g/t, 409.5 m at 0.307 g/t including 111.0 m at 0.514 g/t, 298.5 m at 0.409 g/t including 36.0 m at 0.715 g/t – which is consistent with a large disseminated system. The narrow high-grade results, such as 327 g/t Au over 1.0 m with visible gold at the A-Target, sit inside that system.
Step-Out vs Infill: Two Different Stories
A step-out hole extends the known mineralisation beyond the current resource footprint and, if successful, adds new ground. An infill hole closes the gap between existing holes and, if successful, upgrades the confidence of the resource from Inferred to Indicated. They produce very different news. A step-out result is exciting because it expands the deposit; an infill result is reassuring because it de-risks the resource. The 2026 Tower Mountain programme does both: infill to support a Q4 2026 resource update the Company is targeting at 1.5 Moz Indicated and 3.5 Moz Inferred, and expansion to test the P-Target, about 1,500 m east of the western drilling, which has returned grades and interval lengths statistically indistinguishable from the 47,000 m western dataset.
Comparing Intercepts Across Projects
Comparing intercepts between companies is where investors most often go wrong, because the raw numbers are not like for like. A 300 m interval at 0.4 g/t in a flat-lying deposit in Ontario is not the same as a 300 m interval at 0.4 g/t in a steep vein in West Africa, and the difference is not captured by the grade. The honest comparison uses four adjustments: convert to true width, apply a consistent cut-off, report the same currency of grade (g/t), and state the drilling cost per metre, since C$250-275 per metre at Tower Mountain is among the lowest in Canada. The peer strip-ratio comparison published by the company – 1.8:1 at Tower Mountain against 2.0:1 at Spanish Mountain and 3.0:1 at Springpole – is an example of a like-for-like metric, sourced from Atrium Research.
| Hole / Release | Interval (m) | Grade (g/t Au) | Context |
|---|---|---|---|
| Aug 11, 2026 | 661.5 | 0.554 | Long interval, western contact |
| Sep 22, 2026 | 409.5 | 0.307 | Incl. 111.0 m at 0.514 g/t |
| Sep 28, 2026 | 232.5 | 0.450 | Incl. 33.0 m at 1.383 g/t |
| Oct 5, 2026 | 298.5 | 0.409 | Incl. 36.0 m at 0.715 g/t |
| Oct 13, 2026 | 411.0 | 0.514 | Plus magnetotellurics survey awarded |
| Oct 19, 2026 | 102.0 | 1.178 | New target area |
| Oct 26, 2026 | 336.0 | 0.407 | Continuous mineralisation |
| Oct 26, 2026 | 290.1 | 0.527 | Second long interval |
Red Flags in Drill Result Presentation
Some presentations flatter the numbers. Watch for intercepts quoted only in down-hole length when the true width is far smaller; cut-offs set high enough to exclude the surrounding rock; headline grades that come from a single assay over a centimetre; and results that never make it into a resource estimate. None of these is necessarily dishonest, but they all make the deposit look better than it is. The test is whether the data can be checked: a NI 43-101 technical report, filed March 10, 2026 for Tower Mountain, describes the database underpinning the resource, and the Qualified Persons – William Lewis, P.Geo., Charley Murahwi, P.Geo., FAusIMM, and Tudorel Ciuculescu, P.Geo. – stand behind it.
What Drilling Results Cannot Tell You
Drilling results tell you what is in the ground, not whether extracting it makes sense. They say nothing about the gold price needed, the permitting timeline, the cost of a mine, or the company’s ability to finance one. The 3.5 Moz at Tower Mountain is a resource, not a reserve, and the company is not currently mining or selling gold. The 2026 results are a step toward the Q4 2026 resource update and the initial PEA the Company is targeting for late 2026 or early 2027 – a target, not a promise. See the full results list and the project overview.
��# # R e a d i n g a R e s u l t s T a b l e L i k e a P r o f e s s i o n a l
W h e n a c o m p a n y p u b l i s h e s a t a b l e , t h e t e m p t a t i o n i s t o s o r t b y g r a d e a n d p i c k t h e t o p r o w . A m o r e u s e f u l h a b i t i s t o r e a d f o r p a t t e r n s : w h i c h h o l e s a r e s t e p - o u t s a n d w h i c h a r e i n f i l l s , w h e t h e r t h e w i d e i n t e r v a l s a r e c o n s i s t e n t a c r o s s a d j a c e n t h o l e s , a n d w h e t h e r t h e c u t - o f f m a t c h e s t h e r e s o u r c e e s t i m a t e ’ s 0 . 1 9 g / t A u . A t a b l e w i t h m a n y w i d e i n t e r v a l s a t s i m i l a r g r a d e s i n n e i g h b o u r i n g h o l e s d e s c r i b e s a c o n t i n u o u s s y s t e m . T h e T o w e r M o u n t a i n 2 0 2 6 t a b l e , w i t h m u l t i p l e i n t e r v a l s o f 2 0 0 - 6 6 0 m a t 0 . 3 - 0 . 6 g / t , i s e x a c t l y t h a t k i n d . [ R e a d t h e f u l l r e s u l t s l i s t ] ( / d r i l l - r e s u l t s / ) .
Frequently Asked Questions
Q: What do gold drilling results actually tell investors?
A: A result tells you the gold content of the rock between two depths in one hole and whether the geological theory behind the target was correct. It does not reveal the deposit’s total size, the rest of its grade, or whether it can be economically mined.
Q: How can investors compare drilling results between companies?
A: Convert to true width, apply a consistent cut-off, use the same grade unit and state the drilling cost per metre, since C$250-275/m at Tower Mountain is among the lowest in Canada. A peer strip-ratio table is a more like-for-like comparison than raw intercepts.
Q: What is the difference between step-out and infill drilling results?
A: A step-out result extends mineralisation beyond the current resource footprint and can add new ground. An infill result closes the gap between holes and upgrades confidence, potentially converting Inferred material to Indicated.
Q: What are red flags in drill result presentations?
A: Watch for down-hole lengths quoted without true width, high cut-offs that exclude surrounding rock, headline grades from a single centimetre-scale assay, and results that never appear in a resource estimate. The test is whether the data can be checked in a NI 43-101 report.
Q: Can drilling results prove a mine is economic?
A: No. Results describe what is in the ground, not whether extraction makes sense at a given gold price, the permitting timeline or the cost of building a mine. The 3.5 Moz at Tower Mountain is a resource, not a reserve.