Here's the chemical composition of pennies and dimes in the United States:

Pennies (One Cent Pieces):

* Pre-1982: 95% copper, 5% tin and zinc

* Post-1982: 97.5% zinc, 2.5% copper (copper plating)

Dimes (Ten Cent Pieces):

* Since 1965: 91.67% copper, 8.33% nickel

Important Note:

* The composition of pennies changed in 1982 to reduce production costs due to the rising price of copper.

* Dimes have remained the same since 1965.