This article provides information about precious metals and their various alloys. It gives the reasons why solid gold is never used in jewelry production, explains the purpose of using palladium, and lists many more interesting facts concerning precious metals.
Pure gold is a soft metal and is never used for jewelry making. Jewelry made of pure gold would be neither durable nor stable; it would be easy to scratch with a pin or even with a finger nail. The malleability of gold is why alloys are always used when working with gold. Gold is mostly alloyed with silver, palladium, zinc, cobalt, copper or nickel.
In the US and Europe, the purity of gold is measured in karats while in the countries of the former USSR it is measured by the millesimal standard. The millesimal standard is the three digit number that is sometimes provided after the karatage. The millesimal standard, another way to denote the purity of a metal, refers to the parts per thousand that are pure gold. Gold bars usually consist of pure gold, which is 24-karat gold (999.9). The least pure gold is 9-karat gold (375) or 10-karat gold (417). The most frequently used golds in the jewelry industry are the 14-karat (583) and the 18-karat gold (750).
Pure gold is yellow, but it can easily change its color if alloyed with other metals. Depending on the composition, gold turns almost white when alloyed with palladium, nickel, or platinum, and gold can acquire a slightly red or pink hue when alloyed with copper. Some gold alloys can be of a green, violet, brown, light blue, or even of a black tint.
Currently, white gold jewelry is extremely popular. It looks attractive and expensive, but white gold is more affordable than platinum. Nickel had been a popular choice in gold alloys, but, because nickel allergies are common, jewelers of developed countries now prefer to alloy gold with palladium. Palladium is not allergenic, it is more flexible, it does not lose its color when heated and, finally, it looks more attractive than nickel alloys.
Platinum is white-colored metal; one of the rarest and the most beautiful precious metals used in jewelry. It was discovered relatively recently, in the 18th century, when it was taken to Europe from Peru. Today, platinum is in demand by many industries including technology, chemistry, and jewelry production.
Platinum can be alloyed with gold so during the 20th century, when platinum was the cheaper of the two metals, jewelers used platinum alloys to bring down the cost of gold jewelry. Currently, the situation has reversed: platinum is considered to be one of the most exquisite metals and platinum jewelry is very expensive.
Platinum is appreciated not only for its sophisticated look, but also for its enduring character: it doesn’t change its color over time, it never dulls, and it does not get scratched easily. Platinum that is used in jewelry is 95% pure. Unlike gold, platinum does not need to be strengthened with alloys, and its durability is far greater than that of many other metals.
Palladium is a white-colored metal. Easily alloyed with other metals, palladium is widely used in the jewelry industry. It was discovered in the 19th century in a platinum ore. Today, palladium is extracted from copper and nickel ores.
Palladium itself is rather soft and flexible so it is rarely used as is. Palladium is often strengthen with cobalt or nickel. In jewelry making, it is alloyed with gold to produce a refined and elegant white gold. Only 1% palladium in the alloy is needed to turn the gold white, but the most attractive gold alloys are those containing 50% or 85%.
Silver is a white-colored metal, flexible, and easy to work with. It has been used by gunsmiths and goldsmith for centuries because it could be found in the ore and did not need to be smelted. These days, silver is extracted and smelted from different ores – there are only a few deposits of solid silver remaining in the world. Solid silver is rather heavy but malleable – one gram of silver can yield a 1 mile long string.
In ancient times, silver was used to produce mirrors, coins and jewels. In the Middle Ages, it was in fashionable to make silver dishes. Except for mirrors, which are now made of glass, silver dishes and jewelry are still popular.
Modern silver jewelry usually contains silver alloyed with other metals such as nickel and copper. Similarly to gold, the purity of silver is measured in carats. The purest silver, sterling silver, is 96 or 92.5% pure. Silver is also available in 87.5%, 80%, and 75% silver. Some silver articles are blackened to make them look elegant and antique. After time, silver usually dulls so it needs special care to preserve its original luster.
Copper is a soft and flexible metal of red-gold color. Copper gets its red color from surface oxidation; whereas, unoxidated copper is usually of a slight pink tint. Copper has been used for 9,000 years since civilization began learning about the metal smelting process. Originally, copper was used in alloy with tin to produce bronze weapons and dishes that were much more durable than the pure copper ones.
Naturally, solid copper, as well as copper combined with other metals, can be found in ore, and there are many copper deposits in the world. Jewelers use copper to alloy it with gold. This alloy has a beautiful red color and is very durable for jewelry making.
Bronze has been used since 3,000 BC. Bronze is the result of combining copper with tin. Alloyed with tin, copper becomes tougher, more durable, and more easily-processed. Depending on the percentage of copper used in the alloy, the bronze tints may vary significantly. It can be red (90% copper), yellow (80-85% copper), white (about 50% copper), and even grey as steel when bronze contains less then 35% copper.
The most predominant way of using bronze is casting it. In 3000 BC, bronze replaced copper as the metal for goods and weapons. Bronze weapons were widely used until 2000 BC when iron became the material of choice. Nevertheless, despite iron being cheaper and easier to produce, bronze was still preferred by many for its strength. Bronze armor was more durable than iron, and some countries continued to make bronze helmets until the 19th century.