Global – October 31, 2026 -- Reserve grades at producing silver mines span from about 12.63 g/t Ag at Coeur Mining's Rochester in Nevada to roughly 867 g/t at Hecla's Keno Hill, which shows that no single threshold defines "high-grade" silver.
Fresnillo reported a 2024 silver ore grade of 468 g/t at Juanicipio, an underground operation in Mexico. Hecla's year-end 2025 Keno Hill reserves stood at 25.28 ounces of silver per ton. Rochester's 2025 proven and probable reserves come from a large-tonnage open-pit heap-leach operation.
Grade does not equal recovered metal, and mines sell only recovered metal
A tonne carrying 500 g/t contains five times the silver of a 100 g/t tonne before recovery losses. Mines sell recovered metal, however, not grade. A narrow, discontinuous or hard-to-reach zone can leave a striking assay with limited economic value. Dilution from waste rock can also cut the grade delivered to the plant.
Recovery shifts the outcome sharply. A tonne at 300 g/t with 90% recovery yields far more silver than one where only 55% can be extracted, and treatment and refining terms can reduce payable metal further. Recoverable and payable lead, zinc or gold by-products can lower the effective cost attributed to silver.
Cut-off grades vary by mining method, as Aya's Zgounder shows
Cut-off grade is an economic decision, not a geological label. It reflects mining and processing costs, expected recovery and metal prices. CIM guidance holds that cut-offs vary between properties, operating circumstances and even periods at the same operation. Polymetallic deposits may use net smelter return instead of silver grade alone.
Aya Gold & Silver's 2025 Zgounder disclosure applied a 40 g/t Ag cut-off to open-pit material and 90 g/t Ag to underground material within the same deposit.
Silver-equivalent grades depend on stated assumptions
Polymetallic projects often report AgEq, which converts several metals into an equivalent silver quantity. Metal prices, recoveries and treatment charges can materially change the result. Canadian technical-disclosure guidance requires those assumptions to be explained. Two projects with the same AgEq grade can therefore have different economics.
Higher grade does not automatically lower cost per ounce
If per-tonne mining and processing costs are similar, more payable ounces per tonne improve unit economics and give a mine more room to absorb changes in labour, energy, consumables or metal prices. Narrow underground veins can offset that benefit through selective mining, more development metres, ground-control work and, at depth, higher ventilation, hauling and pumping costs. A large, low-grade surface mine can move a tonne far more cheaply.
All-in sustaining cost (AISC) is a non-GAAP measure and reporting practice varies between companies. It suits existing producers, but applying it to an explorer without a defined mine or production plan would create false precision.
High-grade drill results move juniors' share prices before economics exist
Repeated high-grade intercepts over useful widths can justify further drilling and shape resource expectations. Markets often react to single results before continuity, mineability or economics can be judged. If later drilling fails to connect the mineralization, the gains can reverse quickly. Exploration companies may also dilute shareholders while raising capital to test a discovery.