The Coinage Metals: What Counts as a Transition Metal?
Coins have been in existence for centuries, and their metal composition has changed drastically over time. Coins have been made from all sorts of materials such as iron, copper, bronze and silver, but the coinage metals used as legal tender today consist primarily of a few elements: nickel, copper, and zinc. These are referred to as the “coinage metals”.
But what other elements belong to this broad classification? As it turns out, these three metals are all classified as “transition metals”, which are a group of chemical elements found in the d-block of the periodic table. The coinage metals belong to a subset of the transition elements, known as the coinage transition metals. This article will delve into what constitutes a transition metal, as well as the coinage metals.
What is a Transition Metal?
A transition metal is an element found in the d-block of the periodic table. The d-block consists of elements 58 through 71, as well as elements from 90 through 103. These elements are characterized by the ability to easily form two or more different ions — both positive and negative. Transition metals generally have good electrical and thermal conductivity, along with greater densities than most other elements.
In terms of the coinage metals, they are the elements in the d-block of the periodic table that have historically been used to mint currency. This includes nickel, copper, and zinc, which are often combined in various alloys to create coins.
Coinage Metals in Modern Currency
In modern times, coins have become a bit of a rarity and do not generally serve as legal tender, with paper currency and electronic transactions now comprising the bulk of transactions. However, the three coinage metals remain primary components of the currencies that are in circulation today.
The United States uses copper coated steel coins for its cents (also known as “pennies”) and has done so since 1982. The United States also mints 5-cent coins from an alloy of 25% nickel and 75% copper (commonly referred to as “nickel plating”).
Meanwhile, the composition of 12-sided British coins have changed over time, but in recent years, they have been composed primarily of copper-plated steel along with a cupronickel alloy made of 75% copper and 25% nickel.
The euro consists of eight coins made up of two different alloys: the two, five, ten, twenty, and fifty-cent coins are made from a 75% copper and 25% nickel alloy, while the one, two, and five euro coins are composed of a mixture of copper (89%) and a combination of zinc, nickel, and tin (11%).
Minting Other Alloys from Coinage Metals
The coinage metals are mixed to create alloys of different compositions for minting coins. With the right combination, coins can be made harder or have a degree of tarnish-resistance.
Nickel is a particularly important element in creating coinage alloys as it adds strength and wear-resistance. It is often mixed with copper to form an 80/20 blend of copper and nickel known as cupronickel. As mentioned, cupronickel is the primary alloy used in British five-pence coins.
Zinc is often added to create an alloy with lower melting temperatures and a lower cost of production. Zinc is also a good alloying agent, helping to reduce brittleness and increase strength and durability. This has resulted in a number of variances in alloy and composition over the years, but typically it is used to create a copper/zinc blend (known as bronze) or a copper/nickel/zinc alloy. For example, most American dimes, quarters, and half dollars are composed of a blend of 91.67% copper, 8.33% nickel, and are clad with a layer of pure copper.
The coinage metals constitute a fascinating subset of chemical elements, as they illustrate the importance certain elements have had in shaping currency. Nickel, copper, and zinc remain the key elements within most countries’ legal tender and are an integral part of the currency in circulation today.
These three coinage metals are all considered transition metals, which are elements that can exist in multiple forms and levels of oxidation. The coinage elements often form alloys, combining these elements in precise amounts to create coins of varying qualities in terms of strength and durability.
No matter the composition and form, the coinage metals are a highly important part of any currency, and serve as a reminder of their remarkable importance in the evolution of money and commerce.
