A metal-equivalent grade — CuEq, AuEq, AgEq — converts every metal in an intercept into the economic equivalent of one headline metal, so a copper-gold-silver hole can be quoted as a single 'copper-equivalent' number. Done honestly, it is a fair way to summarise a polymetallic result. Done loosely, it is one of the easiest numbers in the sector to inflate.
Two assumptions sit inside every equivalent grade: the metal prices used, and the metallurgical recoveries assumed for each metal. Aggressive prices or the quiet assumption of 100% recovery on by-product metals can turn a modest primary grade into an impressive equivalent. The tell is when the equivalent grade is far above the primary-metal grade — it means the credits, and the assumptions behind them, are carrying the headline.
Always look for the breakdown. If a company reports 1% CuEq, find the actual copper grade and the by-product grades. If the real copper is 0.4% and prices and recoveries did the rest, you are reading an assumption, not a rock.