Man-made object (metal alloy)

US Penny

Cuprum (Copper: Cu) and Zincum (Zinc: Zn) Alloy

Color: Copper (reddish-brown), though some older pennies can be darker due to oxidation. Luster: Metallic. Hardness: Not applicable in the same way as minerals; its hardness is that of copper (approx. 2.5-3 on Mohs scale) and zinc (approx. 2.5 on Mohs scale). Crystal Structure: Polycrystalline (not a single crystal).

Hardness: Not applicable in the same way as minerals
Luster: Metallic

Identified July 26, 2025More man-made object (metal alloy) →

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Physical properties

Formation & geological history

Manufactured by the United States Mint from metal alloys. The specific penny shown bears the year '2024', indicating it's a modern penny. Modern US pennies (since 1982) are composed of a zinc core (97.5% zinc) coated with a thin layer of copper (2.5% copper).

Uses & applications

Currency for commerce and trade. Also collected by numismatists (coin collectors) for their historical, artistic, and material value, especially rare or error coins.

Geological facts

Before 1982, US pennies were composed of 95% copper and 5% zinc/tin. The change to a copper-plated zinc core was due to the rising price of copper, making the metal value of the penny exceed its face value. Pennies minted in 1943 were made of steel due to copper shortages during World War II, making them easily distinguishable by their silver color and magnetism. Some 1943 copper pennies exist due to minting errors and are extremely valuable.

Field identification & locations

Easily identified by its distinctive coppery color, the profile of Abraham Lincoln on the obverse, and the Lincoln Memorial (or Union Shield for newer designs) on the reverse, along with the denomination 'ONE CENT'. Modern pennies are slightly lighter than pre-1982 pennies due to their zinc core. They are found worldwide wherever US currency is exchanged, though primarily within the United States.

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