RE: Oriole Resources PLC Confirmed Extension of Mbe Sub-Surface Gold System22 Jul 2025 15:59
Short-interval hits ≠ “too small to mine”
The objection mixes two different issues:
Issue What matters in reality
Individual assay widths (e.g. 1 – 3 m at 2–9 g/t Au) Mines are not designed hole-by-hole; an MRE block model averages grades into 10 m, 20 m or 25 m blocks. Narrow high-grade veins often sit inside broader haloes of 0.4–1.0 g/t that carry most of the tonnage. When the block model is constrained by an open-pit shell, what counts is the average diluted grade of each block versus strip-ratio and recovery.
Grade threshold for a new open pit In West Africa over the last decade, bulk-tonnage refractory projects went ahead at 0.6 – 1.2 g/t Au provided: 1) scale was ≥ 1.5 Moz, 2) metallurgical recovery ≥ 80 %, 3) strip ratio reasonable.
Examples:
• Boungou (Semafo, BF, 2017 start-up): 12 Mt @ 1.4 g/t (reserve grade) – but half the ounces sat in 2–5 m wide lenses.
• Sanbrado (West African Resources, BF, 2020): open-pit reserve 0.9 g/t, with many 1–3 m high-grade shoots.
• Kiaka (B2Gold, BF, in build): 2.3 Moz reserve @ 0.86 g/t, POX flowsheet.
How does Mbe stack up right now?
Parameter (MB01-S only, July ‘25 Exploration Target) Current status Typical “go” number for African bulk pits
Contained ounces (mid-case) ~1.1 Moz at 0.86 g/t to only 200 m depth and before MB01-N drilling 1–1.5 Moz minimum
Intercept style Multiple 1–3 m veins grading 2–10 g/t inside 5–30 m zones at 0.4–1.0 g/t Similar to Boungou, Sanbrado, Ahafo South pits
Metallurgy Refractory telluride/pyrite; POX or Albion indicated, ~67 % recovery by CIL alone POX projects (Syama, Kiaka) work at 83–90 % recovery after oxidation
Strip ratio Yet to be modelled – shallow mineralisation (< 50 m) helps < 6:1 preferred
At this early stage Mbe still needs:
infill + MB01-N drilling to lift ounces above ~1.5 Moz;
a scoping‐level metallurgical flow-sheet showing ≥ 85 % overall recovery;
preliminary pit optimisation to prove a competitive strip ratio.
Why the Phase-1 drill programme was enlarged
Forge’s geostatistics flagged that the western 1,000 ppb soil anomaly is not yet inside the domain model. Shifting a few holes west and adding metres is standard practice to avoid an “under-cooked” maiden MRE. It does not imply the system is shrinking; it means they are chasing the edges to avoid leaving convertible ounces off the table.
Bottom line
No, mines are not built just on 1 m‐wide intercepts – but those veins, repeated every few metres in a porphyry package, can deliver an economic diluted grade once modelled.
Yes, a refractory flowsheet is CAPEX-heavier, so Mbe will ultimately need multi-million-ounce scale or a robust gold price to clear the investment hurdle.
At 0.86 g/t and ~1 Moz today, Mbe sits in the same grade/width envelope that has already supported mine builds in Burkina Faso, Mali and Ghana – it just isn’t big enough yet and still lacks a