GOLD

Gold is the chemical element with atomic number 79 and the symbol Au. It belongs to the family of transition metals. Along with silver, platinum, and palladium, it is recognised and regulated as a precious metal by the Swiss Precious Metals Control. Since 2007, China has been the leading producer of gold, extracting 370 tonnes in 2023, ahead of Australia (310 tonnes) and Russia (310 tonnes)*.

Gold primarily comes from mining deposits, although gold panning still allows for the extraction of gold from alluvial deposits. In its pure state, gold is malleable, does not oxidise, and has excellent electrical conductivity.

Different alloys

However, gold is too malleable in its pure state to be used in watchmaking or jewellery, so it is alloyed with other elements to modify its mechanical properties and colour. The choice of elements and their proportions provide a wide range of blends, which can be classified by proportion of their gold content:

  • 999 ‰ = 24ct = +999 ‰ gold
  • 916 ‰ = 22ct = +916 ‰ gold
  • 750 ‰ = 18ct = +750 ‰ gold
  • 585 ‰ = 14ct = +585 ‰ gold
  • 375 ‰ = 9ct = +375 ‰ gold

Shades of gold

In watchmaking, the shade of the alloy is important. Colour standards for gold are established by the Swiss watchmaking industry norms (NIHS). These standards distinguish seven colour shades, ranging from the lightest yellow to the deepest “red,” and are designated as 0N, 1N, 2N, 3N, 4N, 5N, and 6N. This classification does not include grey gold and is purely based on colour, independent of the alloy composition and content. Watchmakers primarily use the colour range between 2N and 5N.

Contrary to popular belief, there is no standardised or legal designation for the colours of gold. However, yellow gold from 0N to 3N, and rose or red gold (some distinguish between them) from 4N to 6N, are commonly referred to.

Gold is mainly alloyed with silver (Ag) and copper (Cu). The amount of copper determines the alloy’s colour, making it more or less red. For example:

  • 2N = 160 ‰ Ag, 90 ‰ Cu
  • 3N = 125 ‰ Ag, 125 ‰ Cu
  • 4N = 90 ‰ Ag, 160 ‰ Cu
  • 5N = 45 ‰ Ag, 205 ‰ Cu
  • 6N = 5 ‰ Ag, 241 ‰ Cu, 4 ‰ Pb

Historically, grey gold alloys were obtained using various additional elements, with nickel, silver, and palladium being the most common. Some grey gold alloys (notably those with silver) have a naturally yellowish colour and often require galvanic treatment (rhodium plating) to achieve a white sheen. Today, palladium alloys are preferred due to their hypoallergenic properties and the fact that they do not require galvanic treatments.

Properties

Gold is malleable, non-magnetic, corrosion-resistant, and has a high density (19.3 g/cm³), giving it mechanical, physical, and aesthetic qualities that have linked it to the world of watchmaking since the dawn of timekeeping.

* Statista.com

The oldest known gold objects date back to around 5000 BC. Gold has long been esteemed as noble and precious in the majority of cultures and throughout history. As a native metal, it is easy to find, especially in alluvial deposits, and its malleability has likely contributed to its long-standing appeal.

Gold’s mechanical, chemical, and aesthetic properties have made it a favourite among watchmakers over the centuries, serving both decorative and technical purposes.

Universally recognised as rare and valuable, gold has historically surpassed the value of platinum since 2008.

Gold can be used to manufacture all external components of a watch (cases, bracelets, clasps, dials, hands, etc.). Its malleability makes it easy to polish and suitable for all types of stone setting. For the same reasons, engravers also value gold, and it is a preferred base for enamelling work. Many movement components can also be made from gold. Oscillating weights and balance screws are frequently made from this metal due to its high density. Less commonly, wheel plates, pinions, and even bridges and mainplates can be made from gold.

Gold is also widely used in galvanic treatments. The surfaces of bridges, mainplates, wheels, etc., are frequently gilded, offering protection against corrosion and oxidation while providing a specific appearance and colour.

Gold is present in tools and certain manufacturing processes (UV-LIGA, DRIE engraving), making it a metal historically inseparable from horology.