Gold, Copper and Silver
We rely on gold, copper and silver every day – you are using them right now as you read this on your computer screen. Gold bars and coins are the popular image of this precious metal, but it has many practical uses.
Why are these precious metals so special and so costly?
We know there’s lots of gold and silver in banks, we’ve seen pictures of expensive gold and silver jewelry and we know that copper is used in coins. But there are many ways we use and rely on each of these metals every day.
- Gold and silver are very good conductors of electricity and heat
- Gold, copper and silver can be alloyed (mixed) with other metals to produce new materials
- Gold, copper and silver are malleable – they are easily shaped, and very ductile – they can be stretched out into very thin wires
- Gold and silver do not chip, flake or corrode
- Gold, copper and silver can be recycled
In your home, gold, copper and silver are used in electronic circuits. It is likely that your television and your computer have gold and copper circuits in them, as well as your PlayStation too. Don’t bother pulling them apart though. The amount will be small, probably in wires thinner than your hair or in very small printed circuits.
Stereo systems sometimes use gold-plated interconnect cables. The gold provides a better contact, and so a better sound. Battery currents in your car and other vehicles rely on copper. There could be some silver on your wrist right now. No, not jewelry. The button batteries used in digital watches contain silver. Similar batteries power a large range of devices.
Silver is also used in some water filters, and although it may seem strange, it is also used in the production of some man-made fabrics. You could be wearing small amounts of silver right now within your clothing. Copper is used in modern medicine to reduce arthritis and joint pain. Gold is used by dentists to make crowns for teeth. Gold, copper and silver are used in hospitals too. Burn creams contain silver, gold leaf is used to treat some types of ulcers, and surgical lasers also use gold and silver.
Need glasses? Photochromatic lenses – those are the ones which go darker when the sun gets brighter – contain gold. Gold, copper and silver are in many places in your everyday life – often where you least expect them.
Who would have thought that at the very top of the Auckland Sky Tower there is a gold-plated ball? It’s there so that if the tower gets struck by lightning, the electricity will strike the ball and be conducted safely to the ground.
Atomic number: 79
Atomic weight: 196.967
Melting point: 1,064 degrees C
Specific gravity: 19.3 when pure
Gold is 19.3 times heavier than an equal volume of water. It’s rare, soft and unreactive.
What is gold?
Gold is a rare metal. Its chemical symbol is Au, named after Aurora, the Roman goddess of the dawn. The purity of gold is described by its “fineness” in parts per 1,000 or by the carat scale, which is parts per 24. The word “carat” derives from the Italian carato, Arabic qirat or Greek keration, all meaning the fruit of the carob tree. Ancient traders used carob seeds as the means to balance the scales in oriental bazaars. Pure gold is 24 carats or 1,000 fine.
The price of gold and other precious metals is quoted in terms of troy ounces. The term “troy” is derived from Troyes, France, a major trading city of the Middle Ages. One troy ounce equals 31.1 grams.
What are the properties of gold?
Pure gold is soft and wears easily. It is often mixed with other, harder metals. A mixture of metals is called an alloy. Gold is very unreactive. This means it is resistant to corrosion and tarnishing. That is why a gold nugget can be buried in the ground for thousands of years and still come up looking shiny.
Gold is malleable (easily shaped) and ductile (can be drawn into very thin wire). A square lump of gold about the size of your thumbnail would weigh an ounce. That ounce of gold can be flattened into a sheet so thin that it would be thinner than a piece of tissue paper, and light could pass through it. It would cover an area about the size of a small bedroom. The same lump of gold can be drawn into a piece of wire 80 km long. That’s long enough to go around a rugby field 23 times.
Where is gold found?
Gold is found as a free metal in nature. It can be found as nuggets or bound up with rock and is too small to see with the naked eye. It is sometimes found in association with other metals.
What has gold been used for in the past?
Gold has been used for ornaments and decoration and as money for over 5,000 years. Gold leaf has been used for the decoration of tombs and statues, cathedrals and temples, fine books, and picture frames since Egyptian times. Many Egyptian burial cases, including King Tutankhamun’s (1352 BC), were gilded with beaten gold. Gold leaf is still often preferred for adorning the domes or ceilings of buildings (such as the Metropolitan Opera House in New York) because its resistance to corrosion means that it will outlast paint by many years.
Gold was made into jewelry long before it was used as currency. The earliest gold jewelry dates from the Sumeric civilization around 3,000 BC. The jewelry was worn by both men and women. Goldsmith’s skills that were understood and mastered at that time are still used today, although some of the techniques have been lost. Gold wedding rings, used in marriage ceremonies since the ninth century, date back to the ancient Egyptian times. The ring is placed on the third finger of the left hand because it was believed that this finger carried an artery leading directly to the heart.
Gold uses today
Besides being a currency, gold has many uses, including:
- Decoration – Gold has been used for ornaments and decoration for more than 5,000 years. Its resistance to corrosion helps it outlast paint.
- Jewelry – Gold has been used in jewelry since as early as 3,000 BC.
- Gold-reflective glass – Gold reflects heat and is so malleable that it is used to coat glass with a thin film, which lets through light, but not heat. The use of reflective glass has reduced cooling and heating costs by as much as 40 percent in some buildings.
- Electronics – Gold is a very good conductor of electricity, and it doesn’t corrode or tarnish at high or low temperatures. It is used in circuits in calculators, television sets, computers, telephones and other electronics.
- Satellites and Communications – Gold is used in satellites as part of their electronic circuits and as a heat shield.
- Aerospace – Because the metal reflects heat, gold is used to protect astronauts, satellites and critical electronic components from damage by hazardous X-rays and solar radiation found in space.
- Medicine – Radioactive gold is used to treat several types of cancer. Gold leaf is used to treat chronic ulcers and is used in surgery to patch damaged blood vessels, nerves, bones and membranes.
- Dentistry – Each year, U.S. dentists alone use about 30 tons of gold for crowns, bridges, gold inlays and dentures because of their high resistance to corrosion and tarnish.
Atomic number: 29
Atomic weight: 63.546(3)
Melting point: 1,084.62 degrees C
Specific gravity: 8.89 when pure
What is copper?
Copper is a metallic element that occurs naturally in the Earth’s crust. The chemical symbol for copper is Cu, which derives from the Latin word cuprum, meaning the island of Cyprus. In the ancient Roman world, most copper was mined in Cyprus. “Copper” is the anglicized version of this word.
Copper is one of only two metals (the other being gold) that has a color other than silver or grey. From the gold of aluminum bronzes to patina green (e.g., the Statue of Liberty), the diverse colors of copper and copper alloys, or metals in which copper is the principle component, make it unique. The most well-known copper alloy families are brass (copper-zinc), bronze (copper-tin) and copper-nickel.
What are the properties of copper?
Copper is malleable (easily shaped), ductile (can be drawn into very thin wire) and a good conductor of heat. It is second only to silver in electrical conductivity and is also corrosion resistant and antimicrobial.
Worldwide resources of copper are plentiful. The ability of this metal to be recycled, again and again, is an important sustainable benefit.
Where is copper found?
Copper can be found underground in the form of copper ore. The main copper ore producing countries are Chile, the United States, Indonesia, Australia, Peru, Russia, Canada, China, Poland, Kazakhstan, Zambia, Zaire and Mexico.
What has copper been used for in the past?
Copper was one of the first metals used by humans. Its earliest use dates back as far as 10,000 years ago, when it was used for coins, ornaments and jewelry.
Ancient civilizations also appreciated copper for its antimicrobial properties. Long before the concept of microbes became understood in the nineteenth century, ancient cultures observed that water contained in copper vessels had little or no visible slime compared to water contained in other materials. Egyptian papyrus records show that, around 2,500 BC, copper was also used to treat infections.
Copper is also attributed with helping to launch the Industrial Revolution.
Copper uses today
Today, there are many uses for copper. However, the four major applications of this metal include electrical wires, roofing, plumbing and industrial machinery.
Wherever electricity flows, connectors are needed. Because of its high electrical conductivity, copper, in its many varieties, is the dominant and favored material for these connectors. It is used in power cables, building wiring, and is an essential component of energy-efficient generators, motors, transformers, and renewable energy production systems such as solar, wind, geothermal, fuel cells and other technologies.
Copper plumbing requires no maintenance, won’t burn or break down, and can last for the life of a building. The Chase Manhattan Plaza in New York, which is 60 stories high and the sixth tallest building in the world, employs about 60,000 feet of copper tubes for its plumbing services.
Building and architecture
Copper has been used for many centuries to produce tube, sheets for roofing and cladding of buildings, and for wire for electrical applications. It is also cast to make faucets and valves, bells and statues that last for hundreds, or even thousands, of years. Copper and its alloys, bronze and brass, serve as decorative and functional elements on some of the world’s oldest and most famous architecture.
In automobiles, copper is used in the production of motors, wiring, radiators, connectors, brakes, and bearings. The average car has approximately 40–45 pounds of copper materials in it. Copper is also used in newer airplanes and trains and in the hulls of boats. Copper-nickel alloys are used to protect boat hulls, as well as offshore platforms, sea water pipe work, and desalination units, from erosion and to reduce the adhesion of marine life, such as barnacles.
Electronics and Communications
Copper is essential to worldwide information and communications technologies. It is part of the infrastructure that enables high-speed data transmission. Its use in silicon chips allows microprocessors to operate at higher speeds with less energy.
The total world production of copper coins absorbs thousands of tons of copper every year. In one recent year, the Royal Mint in London alone minted 700 million bronze and cupro-nickel coins, representing nearly 7,000 tons of metal.
Atomic number: 47
Atomic weight: 107.9
Melting point: 960.5 degrees C
Specific gravity: 10.5 when pure
Silver is more plentiful than gold, and shares many of the same remarkable properties.
What is silver?
Silver is a ductile, malleable, brilliant greyish-white metal. The chemical symbol for silver is Ag, meaning “argentum” – an ancient or poetic word for silver. The term “sterling” denotes a specific weight of silver. This has come to be a term meaning “excellence”.
The price of silver and other precious metals is quoted in terms of troy ounces. The term “troy” is derived from Troyes, France, a major trading city of the Middle Ages. One troy ounce equals 31.1 grams.
What are the properties of silver?
Silver has the highest electrical and thermal conductivity of any metal. It is malleable (easily shaped), ductile (can be drawn into very thin wire) and has antiseptic properties.
Where is silver found?
Silver is found as a free metal in nature or bound up with rock, and is too small to see with the naked eye. It is often, but not always, found in association with gold or other metals.
What has silver been used for in the past?
Silver has had many practical and artistic uses. Because it was found as a free metal and was easy to work, it was put to a variety of uses. The early discovery that water, wine, milk and vinegar stayed pure longer in silver vessels, led to its use as a container for long voyages on land and sea over 2,500 years ago.
Silver uses today
The many properties of silver mean that it is widely used today in science and technology. Each year over 7,000 new patents and papers are published which describe a product or process in which silver is a vital part.
Silver has a range of specialized electrical, mechanical, optical and medicinal properties. Silver is used in solar panels and spacecraft, plumbing and pendants. It has not been an easy metal to replace as new technology reveals additional applications.
The photographic industry uses a large percentage of the silver used each year throughout the world. Silver halides, coupled with dyes, produce colour photographic images. X-ray and black and white photography also rely on silver.
Watches, cameras and calculators use silver in their batteries to provide higher voltage and longer life. Silver oxide-zinc batteries, which have twice the electrical capacity of lead-acid batteries of the same size, are used extensively in aircraft and submarines, where weight is critical.
Silver concentrates the sun’s rays on solar collectors. It is found on the backs of mirrors and protects the heat-reflecting gold film on windows. Under the keys of almost every personal computer is a panel of switches with silver contacts to carry out the countless millions of instructions.
Silver thiosulphate prevents the release of ethylene gas from cut flowers to produce longer lasting blooms destined for export. Silver can be prepared as crystals of silver iodine and seeded into cold cloud to produce raindrops or snowflakes.
Around the home
Water filters used to purify swimming pool and drinking water use silver to prevent the build-up of bacteria and algae.
Microwave cooking is made more appetizing due to a silver alloy coating applied to the bottom of microwave cookware. The surface of the cookware will reach a high temperature quickly, resulting in a browning or crisping of food surfaces. We use the term “silverware” to indicate the best cutlery. Many of the best table accessories such as knives, forks and spoons; jugs, serving dishes and trays are made out of silver.
Silver – and gold – are used in the treatment of arthritis: while gold can be injected into muscles, silver is used to coat arthritis pills.
Burns are disinfected with silver creams, and bones are mended with cement containing antibacterial silver salts. Silver is combined with the powerful chemotherapeutic agent sulphadiazine to produce a drug 50 times more powerful than sulphadiazine alone. It is the most widely used drug for treating burn wounds. Silver is also widely used in dentistry. Silver nitrate can be administered to newborn infants’ eyes to eliminate the incidence of Gonococcal Ophthalmia, a disease which can cause blindness.