My son is five, which means he’s old enough for chores. Right now, he has seven that he’s expected to complete each day. He then earns a dime for each one he completes, and he has to distribute those earnings between three piggy banks: one that he’s going to give to charity, one that he uses to save up for something, and one that he can just take to the store and use for impulse buys. The idea is to start teaching him to save money, and to be charitable with his money. Being five, though, he mostly sees it as a game and as a way to get Star Wars toys.
It’s also led to questions. One evening, as I’m counting out his dimes with him, he asks the question: “What are dimes made of?” Which is a pretty good question. And the only answer I have is “some sort of metal”. Zinc, maybe? I don’t know.
And so I turn to the United States Mint. Because if anyone can answer that question, it’s the people who actually make the coins.
What Are US Coins Made Of?
Unsurprisingly, all of the various denominations of United States coins are made of metal. The exact composition varies by coin, however.
- The Lincoln Penny (One-Cent Coin) has been made of copper-plated zinc since 1982. The entire coin weighs 2.5 grams – 2.4375 grams of which is zinc, and 0.0625 grams of which is copper. This hasn’t always been the case, though. From 1793 until 1962 the coins were primarily made of copper, ranging anywhere from 88% to 100% depending on the year.
- The Jefferson Nickel(Five-Cent Coin() is a 5 gram coin made of “cupro-nickel” – an alloy of 25% nickel and 75% copper. There was an earlier silver five-cent coin called a “half disme” (pronounced “dime”) that was produced until 1873.
- The Dime (Ten-Cent Coin) is a 2.268 gram coin made of “cupro-nickel” as well, although it is only 8.33% nickel.
- The Quarter Dollar (Twenty-Five-Cent Coin) is a 5.670 gram “cupro-nickel” coin, with the exact same proportions of nickel to copper as the dime – 8.33% nickel.
- The Kennedy Half-Dollar (Fifty-Cent Coin) is a 11.340 gram coin, made of the same 8.33% nickel “cupro-nickel” as the dime and quarter. Interestingly, even though they are legal tender, the mint states that they are “produced as collectibles, not for everyday transaction”.
- The Native American $1 Coin. First of all, I did not know this was the official name – I’d always heard them called the “Sacagawea Dollar”, because Sacagawea appears on the face of the coin. It’s an 8.1 gram coin made of “manganese-brass”, an alloy that is 88.5% copper, 6% zinc, 3.5% manganese, and 2% nickel. Much like the half-dollar, this coin is legal tender but primarily produced as a collectible.
- The Presidential $1 Coin is identical to the Native American $1 coin except for the design on the face.
- There are also an assortment of uncirculating gold, silver, and platinum coins produced by the US Mint. These are generally not used for legal tender.
How Are The Coins Made?
There are four US Mint Facilities that manufacture coins for the country:
- Philadelphia, which performs “sculpting-engraving of U.S. coins and medals; production of medal and coin dies; production of coins of all denominations for general circulation; production of regular uncirculated coin sets; production of commemorative coins as authorized by Congress; production of medals; and conducting of public tours”
- Denver, which performs “production of coins of all denominations for general circulation; production of coin dies; production of regular uncirculated coin sets; production of commemorative coins as authorized by Congress; and the conducting of public tours; and storage of gold and silver bullion”.
- San Francisco, which performs “production of regular proof coin sets in clad and silver; production of commemorative coins as authorized by Congress”.
- West Point, which performs “production of all uncirculated and proof one-ounce silver bullion coins; all sizes of the uncirculated and proof gold bullion coins; one-ounce platinum bullion coins; the 24-karat one-ounce American Buffalo Gold Bullion Coin; and commemorative coins as authorized by Congress; and storage of silver, gold and platinum bullion.”.
Regardless of which mint makes the coin or which specific coin is being made, the general process is the same. First, blank discs of metal (called “blanks”) are “punched from coiled strips of metal about 13 inches by 1,500 feet in a blanking press” – except for the penny, which just has the blanks pre-made. The blanks are then run through an annealing furnace to soften them up, washed and dried, and then upset – meaning they have a rim raised around their edges. The blanks are then stamped with the dies, turning them from blanks to coins, and then inspected to make sure they were stamped correctly. If you’d like a little more detail, the US Mint has a virtual tour of the process available.
Oh, and those grooves on the edge of the coin? That’s called “reeding“. Originally they were cut onto the coins to make counterfiting more difficult, and to make it obvious if someone was filing (or “shaving”) the coins in an effort to get a little precious metal off the coin before circulating it once more. Clearly we don’t circulate gold and silver coins any more, but the reeding is retained for tradition, and as a way to make it easier for the visually impaired to tell similar sized coins apart.
That’s Cool. But What About Paper Currency?
Currency notes are printed by the Bureau of Engraving and Printing, part of the U.S. Department of the Treasury. And someone there must have a good sense of humor because the web address for the bureau is “www.moneyfactory.gov”, which I find charmingly direct. They print the notes in $1, $2, $5, $10, $20, $50, and $100 denominations. Larger notes ($500, $1,000, $5,000. and $10,000) are still legal tender, but have not been printed since 1945 and have not been issued since 1969.
The notes are printed on a special currency paper composed of 75% cotton and 25% linen, with specialized security threads and watermarks embedded in the paper for everything but the $1 note (along with a 3-D security ribbon for the the $100 note). The actual printing is a combination of green ink, black ink, color-shifting ink, and metallic ink – obviously, exact details of manufacture of the ink are not made public. Much like the U.S. Mint, the BEP has a virtual tour of the currency-making process if you’d like more details.