Jenn asks: What are the physical and chemical properties of the metals choosen to produce certain coins and why were they choosen?
The first “coins” were cows and chickens and handicrafts that had to be carried, pushed or driven to market or to a potential buyer. Though barter never really disappeared, it was replaced in large part by coins. The invention of coins was revolutionary. It allowed trade to flourish, promoted innovation in architecture, science, medicine and, of course, economics.
The key to its success was that coins were looked upon as a store of value. In order to gain acceptance by the public the coins had to be durable (a lot more durable than a cow). Gold was the only material known to the ancients that wouldn’t rust, corrode or melt in the hot sun and was significantly rare to gain acceptance. Silver, though not as durable, became a subsidiary coinage metal. Gold and silver are usually found together, in fact, the first coinage metals was “electrum”, an alloy of gold and silver.
In order to quantify the amount of gold in a coin, an official seal was punched into a gold disk. This saved time, the coin didn’t have to be weighed each time it was spent, and there was an official guarantee, which enhanced acceptability. Even small amounts of gold were valuable so small transactions (i.e. a glass of wine) were difficult. Bars of copper were introduced with equivalent value to a few shavings of gold but they proved to be to heavy and difficult to move around. Governments introduced token coinages in copper as a convenience and to make them acceptable, pledged to redeem specific numbers of copper coins for gold or silver.
During the time of Ancient Greece few base metal coins were minted, probably because the centers of government were too diffuse. The populace preferred small change in the form of tiny silver coins. Base metal token coins flourished under Imperial Rome (14 BC – c.450 AD). The copper/bronze coinage of As, Dupondius and Sestertius were successful for hundreds of years.
The triad of base metal, silver and gold coins continued until modern times. Today, there are no circulating precious metal coins. Modern economies see money as representing goods and services and it no longer matters what form money takes as long as there is acceptability. Paper money, checks, coins, credit cards, debit cards are all money as long as you can walk out the door with the goods.
Today, the choice of coinage metals is more dependent on its electrical properties than its rarity. The coins have to work in vending machines and telephones. In the United States, mimicking the look of silver coins was considered important when the minting of 90% silver coins ceased in 1964. The question of acceptability was raised again. For coins that were previously silver, a sandwich of copper-nickel over a pure copper core was devised so the coins had a similar appearance to their silver cousins. The reeded edge, a security device that was part of silver coinage, remained to keep the coins looking the same.
An interesting story surrounds the new “gold” colored dollars. Since 2000, the dollar is minted from an alloy of copper, nickel and manganese and was designed to replaced the failed Susan B. Anthony dollar. The challenge for the Mint was to create a dollar that looked different (people complained that they confused the SBA dollar with a quarter) but had the same electrical properties. Both coins are the same size and weight and work the same in vending machines.