Interesting facts about gold: fineness and alloy explained clearly

Fineness, carat, alloy - anyone who delves into the fascinating world of gold will quickly come across technical terms that are not always easy to categorise. A solid basic knowledge of gold types helps to understand the differences and make the right choice for jewellery or investments. How exactly is the gold content determined? Why are there different gold alloys and which are best suited for high-quality jewellery?

The most important facts in brief

• The fineness determines the gold content: the higher the fineness, the purer the gold - expressed in carats or thousandths of a carat.

• Higher carat numbers mean more value, but also more softness: 24 carat is pure gold, 14 and 18 carat are more common for jewellery because they are harder and more resistant.

• Alloying makes gold suitable for everyday use: gold is mixed with other metals such as silver or copper to make it more robust and more variable in colour.

• Different gold colours are created through additives: White gold, yellow gold, rose gold - depending on the mixture, the appearance changes.

Gold alloys - what's behind them?

Pure gold is so soft that it can be easily pressed in with a fingernail or scratched with a knife. Even simple mechanical stress can leave its mark. To make it more resistant, it is therefore enriched with other metals. This realisation is not new: even in ancient Egypt, gold was mixed with other metals to make it more stable. The Romans also developed coins made of alloyed gold to improve durability in everyday use. In the Middle Ages, specific mixing ratios were tested to make gold jewellery more robust - a practice that was perfected over the centuries.

Did you know? The technical term for mixing gold with metals such as silver, copper or palladium is ‘alloying’ (Latin ‘ligare’, to combine, unite). The alloy not only changes the hardness, but also the colour of the gold.

Gold colours: What factors influence the colour?

Why doesn't gold always look the same colour? The colour tone depends on the metal mixture - and this can create amazing effects:

Yellow gold
Mixture of gold, silver and copper in a balanced ratio - classic warm gold tone.

White gold
Alloy with palladium, silver or nickel - created by removing the yellow colour tone, often rhodium-plated for extra shine.

Rose gold
High copper content provides a warm reddish colour, varying depending on the mixing ratio between rose and red gold.

Green gold
Also contains silver and small amounts of cadmium - rare and unusual in jewellery.

Blue gold
Combination with indium or gallium - especially for designer jewellery, but more brittle than other alloys.

Black gold
Achieved by surface treatment with rhodium or cobalt - a striking, rare look for avant-garde designs.

Carat - meaning and classification

The term ‘carat’ has a fascinating origin that is deeply rooted in the history of trade. It is derived from the Arabic ‘qirat’, a term that refers to the seeds of the carob tree. These seeds served as natural measures of weight in ancient times; they weigh an astonishingly consistent 0.2 grams and are - were - therefore reliable for weighing precious metals. Traders in the Mediterranean developed a standardised system for determining the fine weight of gold.

Over the centuries, the carat system was refined and finally transformed into the 24-part scale, which is recognised worldwide today and indicates the fine gold content of an alloy.

The most important carat values and their use:

• 24 carat (999 gold) - 99.9 % fine gold, very soft, mainly used for bars and coins.

• 22 carat (916 gold) - 91.6% fine gold, high-quality coins and traditional jewellery in India and Arab countries.

• 18 carat (750 gold) - 75% fine gold, high-quality jewellery with an intense gold tone, ideal for the finest jewellery.

• 14 carat (585 gold) - 58.5 % fine gold, durable jewellery with a good balance between hardness and gold content, often used for everyday jewellery.

• 9 carat (375 gold) - 37.5 % fine gold, robust and inexpensive jewellery, often used in costume jewellery.

Good to know

The higher the carat number, the purer and more valuable the gold - but at the same time the softer it is. This is why 14 or 18 carats are ideal for jewellery: they offer a perfect blend of aesthetics, value and durability.

Frequently asked questions (FAQ) - Gold, alloy, carat

1. Which gold alloy is best for jewellery?

14 carat (585) and 18 carat (750) are ideal as they are robust, retain their value and are visually appealing.

2. What is the difference between carat and fineness?

Carat indicates the gold content in 24 parts, while the fineness is given in thousandths (e.g. 750 = 75 %).

3 Why are there different colours of gold?

The addition of metals such as copper, silver or palladium changes the colour - yellow gold, white gold and rose gold are the best known variants.

4. which carat number is the highest?

24 carat is the highest purity with 99.9% fine gold, but too soft for jewellery.

5. How do I recognise the gold quality of my jewellery?

Through a hallmark (stamp), which indicates the purity, or through professional testing by an expert.