As previously mentioned, all these coins denominations are now composed of copper - nickel clad with an outer layer of a 75% copper, 25% nickel alloy and a pure copper core. Nickels are made of the same copper-nickle alloy but without the copper core.
The penny's composition was altered in 1982 from 95% copper 5% zinc, to the current 97.5% zinc, 2.5% copper mix. This was done as a cost cutting measure and to make the penny lighter in weight.
The 25-cent (quarter), 10-cent (dime), five-cent (nickel) and one-cent (penny) pieces are the coin denominations commonly in use today. Half-dollar and dollar coins continue to be issued but rarely circulated in everyday commerce. Foreign coins exist in all sorts of denominations.
U.S. coin denominations issued in the past but no longer in use include the half-cent, two-cent, three-cent and 20-cent copper pieces and a small silver coin called a half-dime. Gold coins in denominations of $1, $2.50 ("Quarter Eagle"), $3, $5 ("Half Eagle"), $10 ("Eagle"), and $20 ("Double Eagle") were issued from time time from 1793 to 1933.
Silver half-dollars have been minted in large quantities since 1793 and placed in popularity with introduction of the Kennedy half-dollar in 1964. Silver-less half-dollars were first introduced in 1971.
Silver dollars have been issued at various time since 1793, were discontinued in 1933, and then re-introduced in 1971 in the form of the silver less Eisenhower dollar. The Eisenhower dollar was replaced in 1979 with the silver less Susan B. Anthony coin, in honor of the famed women suffrage pioneer.
A new dollar coin replaced the Susan B. Anthony coins. That coin potrays Sacagawea, the Native American Women who contributed to the success of the Lewis and Clark expedition. The coin is golden in color and make from a manganese brass metal alloy.