Gold alloys

Gold alloys © Own image

585 gold, 750 gold or 916 gold?

Gold is a very soft metal. Pure gold is therefore unsuitable as a material for jewelry production or in dentistry. Instead, gold alloys are used. An alloy is a mixture of different metals that are melted together.

Alloys influence the properties of gold

Gold alloys are metal mixtures in which gold is usually the main component. By adding other precious or non-ferrous metals, ranging from silver, nickel, zinc, copper to platinum, iridium, tungsten and titanium, physical and optical properties such as color, hardness, density or tensile strength can be influenced.

Colored gold alloys are known, with which the hue of the gold is deliberately changed , so that red gold, white gold, green gold and other colored gold is created. Even blue gold was experimented with at the turn of the century, in which iron was added. Depending on the proportion of gold and the type and amount of metals added, the various alloys then also differ in value. Physical difficulties in processing by the specialist are also reflected in the price.

Truly pure gold, on the other hand, is used today primarily in investment gold products, i.e. bullion coins - such as the Golden Vienna Philharmonic - or gold bars, which consist of 99.9% - or 999.9‰, as it is correctly stated - pure gold.

At the same time, this does not mean that every bullion coin consists of pure gold. The well-known Krugerrand, for example, has a gold content of only 91.6%, and even older coin gold often consists of alloys with a gold content of less than 90%.

Most often, copper is used to alloy coin gold, which on the one hand gives the coin a slightly warmer hue, but also makes it harder for an everyday use. This higher abrasion resistance, in addition to the technical reasons in the extraction of gold from used gold, is also a reason why ancient coins were not made of fine gold.

What are the gold alloys?

Anyone who wants to sell old jewelry, coins or other items made of gold, must therefore find out what gold alloy a piece is made of. In the course of time, a variety of different gold alloys appeared, whereby there are relatively common as well as rather rarer alloys.

The age and origin of the gold also very often plays a role here: because here in Central Europe, completely different gold traditions developed than, for example, in the Middle East or in Asia, which also has an effect on the alloys used.

999 gold - 24 carat: gold content 999‰ thousand parts.

This gold alloy is equivalent to 24 karat or fine gold. According to LBMA regulations, gold bars must have at least 995‰, although 999.9‰ is the current standard of all renowned bar manufacturers. Both the smaller bars and gold coins, for example the Maple Leaf or the China Panda, or even the Vienna Philharmonic are available as 999 gold. The gold content here has a proportion of 99.9 percent as a minimum.

986 gold - 23.6 carat: gold content 986‰ thousand parts

This alloy with a gold content of 98.6% is known as ducat gold. The first ducats were minted in Venice in the 13th century and from there spread throughout Europe. The famous Austrian gold ducats are still made of this gold alloy today.

1 Ducat Gold coin
1 Ducat gold Austria | Gold coin 260,50 

To the gold is added 1.4% copper and silver. Today, this coin gold alloy is hardly used. For the manufacture of jewelry, the 23.6 carat gold is still much too soft.

965 gold - 23 carat: gold content 965‰ thousand parts.

Alloys with 96.5% gold content are especially common in Southeast Asia and known to us as Thai gold. Although the alloy is basically still too soft for jewelry production, gold jewelry in Thailand is made of 23 karat gold. Also because the jewelry is seen mainly as a financial investment. European gold jewelry with 14 or 18 carats, on the other hand, is considered inferior there.

950 platinum 950‰ thousand parts

Should you have a piece with a hallmark Pt 950, it is most likely a platinum alloy. Unlike gold jewelry, platinum jewelry usually has a purity level of 95%, because due to its density and weight, platinum is much more resistant than other jewelry metals.

916 gold - 22 carat: gold content 916‰ thousand parts.

Gold with a content of 91.6%, which corresponds to 22 carats, is used for jewelry production in many countries where gold has a traditionally high value. Especially in India and the Middle East, 916 gold is the common alloy for gold jewelry, as a certain degree of hardness is already achieved while still retaining the characteristic hue of pure gold.

900 gold - 21.6 carat: gold content 900‰ thousand parts

Gold with a proportion of 90% was particularly popular for trade gold coins, such as crowns, guilders or the imperial gold coins from the German Empire, and is considered the classic coin gold in Europe and the USA. In the Orient, however, 900 gold is also used for the production of high-quality jewelry.

875 gold - 21 carat: gold content 875‰ thousand parts

Gold with a fineness of 875 is especially common in some Arab countries. Here, gold at 21 carats is alloyed mainly with copper.

750 gold - 18 carat: gold content 750‰ thousand parts

750 or 18 carat gold is the classic alloy for high quality gold jewelry. By adding copper, silver, platinum, the 750 jewelry gold is available in very many colors, for example as white gold, yellow gold or red gold.

585 gold - 14 carat gold: gold content 585‰ thousand parts.

585 gold is the most widely used gold alloy for jewelry worldwide. The gold content of 58.5 percent corresponds to 14 carats. This gold alloy is also available in many color variations, depending on which other metals are alloyed.

Low-grade gold alloys may not be sold as gold jewelry in Austria according to the Hallmarking Act.

375 gold - 9 carat: gold content 375‰ thousand parts.

An alloy with only 37.5% gold is no longer seen by many - and by the Austrian hallmarking law - as a real gold alloy, but only as a gold-bearing metal, since the gold content is less than half. Also in Switzerland pieces of 375 gold and below may no longer be sold as gold jewelry, but only as " guarantee metal".

333 gold - 8 carat: gold content 333‰ thousand parts

The 333 jewelry gold is the lowest of the common finenesses. The alloy has only more than a third of gold, usually the rest is mainly copper. Use 333 gold jewelry range for chains, rings, bracelets, earrings and other low grade gold jewelry. The low percentage of fine gold also means that such jewelry tarnishes and discolors quickly. So that these pale gold colors still find the taste of buyers, these are re-gilded with a higher fine gold color.

Common gold alloys for jewelry

What are the most common gold alloys for jewelry? In Austria, jewelry is mostly made of 585 gold, which is an alloy with 58.5% pure gold. In Germany, the less expensive 333 gold jewelry is also common, so it has a gold content of only 33.3%. In Italy and the Balkans, on the other hand, jewelry made of 18-carat gold, i.e. a 750 alloy, is more common.

How is the gold content determined?

In gold jewelry, the fineness is usually stamped in the form of a hallmark. To check the correctness of hallmarks, the acid test, also known as the line test, is usually used. The gold piece to be tested is rubbed on a touchstone, a slate, in such a way that a clear line remains. Various test acids are then applied to this test line one after the other. Each alloy has its own test acid, which consists of a mixture of hydrochloric acid and nitric acid (aqua regia). If the abrasion on the touchstone becomes distorted or discolored, the alloy is below the tested fineness; if the line remains unchanged under the influence of the acid, the gold content corresponds to the respective carat activity.

Dental gold alloys

Dental gold © own work

Even in dentistry, pure gold is not used, but dental gold alloys that give the material the necessary hardness. The yellow dental gold usually consists of high-quality dental gold alloys with up to 14 carats, alloyed with silver, platinum and palladium.

White dental gold, on the other hand, can be alloyed only with platinum, with silver and palladium, or with steel and titanium. While old dental gold-platinum and silver-palladium alloys can be sold as scrap gold, dental steel-titanium alloys are almost worthless.

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