Up to 82% Gold and 58% Silver Extraction; Finer Crush Improves Recovery; Agglomeration Not Required
HERMOSILLO, MX / ACCESS Newswire / September 25, 2026 / Tocvan Ventures Corp. (the "Company" or "Tocvan") (CSE:TOC)(OTCQB:TCVNF)(WKN:TV3/A2PE64) announces final results from an independent closed-circuit column leach metallurgical program on a bulk composite from the Gran Pilar Gold-Silver Project, Sonora, Mexico.
The work was completed by Laboratorio Tecnológico de Metalurgia S.A. de C.V. (LTM ISO/IEC 17025:2017 and ISO 9001:2015) on approximately 1,037 kilograms of bulk material crushed to two sizes (P80 3/4" and P80 3/8"), tested both agglomerated (Portland cement) and non-agglomerated. Four 6-inch-diameter columns, each loaded with ~146 kg of ore to ~5 metres height, were operated for 84 days (3-day cure, 77-day leach, 4-day wash, 3-day drain) at a target irrigation rate of 12 L/h/m² and 1 g/L NaCN. The tests were completed to optimize recovery strategy for the pilot facility as it nears completion.
Key Highlights
Head grade of the composite: ~2.19-2.21 g/t Au and ~14.9-15.4 g/t Ag
Bottle-roll tests (100% minus 10 mesh, 72 hours): Recovery of 89-91% Au and ~73% Ag.
Closed-circuit columns after 77 days of leaching:
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P80 3/8": 81.6-82.3% Au and 54.8-58.0% Ag
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P80 3/4": 75.4-76.4% Au and 49.1-52.4% Ag
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Finer crush improved gold extraction by about 6 percentage points.
Agglomeration did not materially improve gold or silver extraction and increased cyanide consumption.
Non-agglomerated columns used less NaCN (1.08-1.29 kg/t vs 1.55-1.74 kg/t). Lime consumption was similar (~3.65-3.84 kg/t CaO).
Copper dissolution was low (3.3-5.4%).
Ag: Au ratio of ~4.7-5.0.
Results are a clear improvement on the 2023 bulk-sample heap test (62% Au over 46 days on coarser material) and support heap-leach processing for the 50,000-tonne pilot facility targeting first production in Q4 2026.
Column Leach Summary
Column | Crush (P80) | Agglomerated | Au ext. (%) | Ag ext. (%) | Cu ext. (%) | NaCN (kg/t) | CaO (kg/t) |
CL-01 | 3/4" | Yes | 76.41 | 52.44 | 4.20 | 1.55 | 3.84 |
CL-02 | 3/4" | No | 75.36 | 49.12 | 5.13 | 1.08 | 3.67 |
CL-03 | 3/8" | Yes | 81.63 | 54.84 | 3.26 | 1.74 | 3.83 |
CL-04 | 3/8" | No | 82.25 | 57.99 | 5.36 | 1.29 | 3.65 |
Cycle includes 77 leach days + 4 wash + 3 drain. Calculated heads correlated well with assay heads.
"These closed-circuit column results give us a much clearer picture of how Gran Pilar material will perform under heap-leach conditions as we finish the 50,000-tonne pilot," said Christopher Gordon, CEO of Tocvan. "Gold extraction of 75 to 82 percent at commercial crush sizes, without agglomeration, is a clear improvement on the 2023 bulk test and supports first production later this year.