You can find most popular coin collecting phrases in this coin glossary.
zinc - cheap metal used to mint coins. It was used from 1982 tom int US 1 cent penny as copper-plated zinc, 97.5% zinc. Also used in combination with steel, as with zinc plated steel cent of 1943, which was minted due to shortages of copper during WII and in brass coins, which look similar to gold. Modern US 1 dollar coins are made from brass (alloy of copper and zinc) and nickel to immitate gold.