Discover Copper Online

Spring 2000

New Coins Mostly Copper

Both sides of the new "Connecticut" quarter; all of the 50 new quarters, one for each state, are 91.67% copper.

The new "Golden Dollar Coin" and the 50 new quarters, one for each state of the union, are mostly copper. The U.S. Mint began circulating the new golden-hued dollar, which is 88.5% copper, in January. The Mint projects that production of the new dollars could reach 1 billion this year, far surpassing production of the Susan B. Anthony (SBA) dollars, of which only 900 million were coined in 21 years.

The new dollar coin has a copper core. The gold color comes from outer alloy layers metallurgically bonded to the core. The alloy is a manganese brass, a golden-colored material composed of 77% copper, 12% zinc, 7% manganese and 4% nickel.

Electromagnetic Signature Matched

The new dollar replaces the unpopular SBA dollar, which many confused with quarters. Because many thousands of electrically activated vending machines accept the SBA dollar, it was essential that the new dollar match the SBA's electromagnetic dimensions and signature. It took 30 months of R&D to achieve this requirement. Designing the alloy composition of the dollar fell to Dennis Brauer, a metallurgist and vice president of Quality and Product Development at Olin Brass, East Alton, Illinois. Olin Brass is a leading U.S. copper alloy producer that has for many years been an approved supplier of coinage strip to the Mint. PMX Industries, Cedar Rapids, Iowa, also furnishes strip for the new coin.

Brauer faced a difficult metallurgical task. "Our objective was to mimic as closely as possible the electromagnetic footprint and the weight of the SBA dollar while at the same time imparting a golden color. Any one of those parameters is relatively easy to satisfy; the really hard part is getting all three correct at the same time.

"The combination of electromagnetic footprint - in particular, the coin's electrical conductivity - and color was the most difficult objective to achieve. The Mint called for a color between that of 14- and 22-karat gold. We knew the electromagnetic footprint of the SBA, and from the technical literature and our experience with copper alloys, we knew what effect various alloying elements would have on these parameters.

"We had to select alloying elements that reduce copper's conductivity. All elements do that, but only nickel and manganese will remain in the necessary solid solution in copper over the range of concentrations of interest in the coin.

"Copper alloys containing nickel are silvery in color, so nickel alone wouldn't work. Copper-manganese alloys, of which there aren't very many, retain more of copper's red. There is, for example, an alloy called manganin containing 87% copper and 13% manganese that has high electrical resistivity and is somewhat pinkish in color. We discovered that by using a combination of nickel and manganese we were able to get very close to the conductivity required in the new dollar."

"Gold" from Zinc

"We also knew that zinc imparts a yellow color to copper alloys, as it does in brasses." Brauer continued, "Our approach, therefore, was to combine copper with manganese, nickel and zinc to simultaneously satisfy all the required properties. We tested many compositions before we arrived at the combination the Mint accepted."

Metallurgically, the new alloy is a manganese brass. It's a single-phase alloy much like ordinary cartridge brass. The alloy is metallurgically stable; micrographic examination reveals no evidence of precipitation. In addition to having the specified electromagnetic properties and the proper color, the alloy's density is very close to that of the copper-nickel it replaces.

The new alloy also has many of the other properties desirable in coinage. Its high malleability enables it to be embossed to produce clear, sharp images. It is durable, yet not so hard as to wear stamping dies too much. Like other copper alloys, it is also relatively tarnish and corrosion resistant, and it has a pleasant ring when struck.

The obverse (heads) of the new dollar coin was designed by American sculptor Glenna Goodacre; the reverse (tails) was designed by Thomas D. Rogers, Sr., a sculptor and engraver with the Mint. The 17 stars on the reverse represent the number of states in the union at the time of the Lewis and Clark expedition. They surround a soaring eagle meant to symbolize the optimism and freedom represented by the grand exploration.

Circulation of the new dollar began at the 3,000 Wal-Mart stores and Sam's Clubs, which make change with the coins. Those who want to obtain uncirculated dollars can order them by calling 800/USA-MINT or accessing the Mint's informational site. The golden dollars come in 25-coin rolls for $35.50 and bags of 2,000 coins for a charge of $2,190.

Olin Brass: 618/258-2000
PMX Industries: 319/368-7700

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