NARRATOR：

Listen to part of a lecture in a materials science class.

MALE PROFESSOR：

So what's the first thing that comes to mind when we talk about uses for copper? Tammy?

FEMALE STUDENT：

The penny? It's made of copper...

MALE PROFESSOR：

Okay, good one... but what's a one-cent coin worth these days?

You might get back change, like if you go to the store and give the cashier five dollars for something that costs four dollars ninety-eight cents, you'll get two cents back... but two cents doesn't buy much.

The value of the penny in terms of what it'll buy has gotten so low that there's actually a move afoot to eliminate the coin from U.S. currency.

But there's more to it. As Tammy implied, the penny looks like it's solid copper.

It's reddish orange, with a bright metallic luster when it's new; but that's just the copper plating.

The penny's not solid copper; in actuality, it's almost 98 percent zinc.

But, um, given the rising value of both these metals, each penny now costs about 1.7 cents to produce... so it generates what's called negative seigniorage.

Negative seigniorage is when the cost of minting a coin is more than the coin's face value.

Even though the penny generates quite a bit of negative seigniorage, there's concern that if it is eliminated, we'll need more nickels— because more merchants might start setting prices in five-cent increments... four dollars ninety-five cents, and so on.

So we need a trusty five-cent piece that can be minted economically.

But the nickel's negative seigniorage is even worse than the penny's... each nickel costs the U.S. Mint ten cents to produce!

Also, some of us are pretty attached to pennies for whatever reason... nostalgia, and then there's collectors... and people, if they see a penny on the sidewalk, they'll pick it up and think, "It's my lucky day."

Another scenario is that without pennies, merchants, instead of charging four-ninety-eight, might round up the price to an even five dollars.

So consumer goods would become slightly more expensive.

But, on the other hand, some cash transactions would be more convenient for consumers.

And, as I said, the government would save money if pennies were eliminated.

FEMALE STUDENT：

But wouldn't the copper industry suffer financially if the U.S. government stopped buying copper to make pennies?

MALE PROFESSOR：

[Leadingly, trying to get the student to see her mistake] But how much copper do pennies actually contain?

FEMALE STUDENT：

[repeating the question to herself] How much... [realizing her mistake] Oh, got it... right.

MALE PROFESSOR：

So, what else comes to mind when you think about copper? [beat—no takers] What else is copper used for?

FEMALE STUDENT：

I know that copper can be shaped into all sorts of things: sheets... tubing... My cousin's house has a copper roof.

MALE PROFESSOR：

Yes, like gold and silver, copper's extremely malleable, but it's not a precious metal; it's far less expensive than gold or silver.

It's also a superb conductor of electricity, so you can stretch it into wires, which go into appliances and even car motors.

Copper also has superior alloying properties—[clarifying] it's, y'know, when it's combined with other metals.

For instance, how many of you play a brass instrument, like a trumpet or trombone?

Well, brass is an alloy of copper and zinc. If your trombone was made of pure copper or pure zinc, it wouldn't sound nearly as beautiful as a brass trombone.

Another alloy, a combination of copper and nickel, resists corrosion... it doesn't rust, even with prolonged exposure to water.

FEMALE STUDENT：

But what about the Statue of Liberty, in New York Harbor? It's made of pure copper, but it turned green. Isn't that a sign of corrosion?

MALE PROFESSOR：

Indirectly. If copper's exposed to damp air, its color changes from reddish orange to reddish brown.

But, in time, a green film called a "patina" forms, and the patina actually serves to halt any further corrosion.

It's one reason that ship hulls are made of copper-nickel alloys.

These alloys are also hard for barnacles to stick to. If these little shellfish adhere to the hull of a ship, it produces drag, slowing the vessel down.

Copper's also a key material used in solar-heating units and in water-desalination plants, which are playing increasingly important roles in society.

Bottom line? If you're a copper miner, you won't lose any sleep should the penny get—if you'll excuse the expression—pinched out of existence.