Base elements → Materials → Metallic materials

GOLD

Table of main properties of gold

Property Typical Value Remarks
Density ~19.3 g/cm³ Very high
Young’s modulus (E) ~70–80 GPa Low to moderate
Tensile strength ~100–300 MPa Depends on alloy
Hardness (HV) ~20–150 HV Very low (pure gold is soft)
Thermal conductivity ~310–320 W/m·K High
Electrical conductivity ~45–48 MS/m High
Thermal expansion ~14–15 ×10⁻⁶ /K Moderate
Melting point ~1064 °C Pure gold
Magnetism No Non-magnetic
Corrosion resistance Excellent Does not oxidize
Machinability Excellent Very easy to work

Gold is a precious metal that has been used in watchmaking for several centuries, primarily for its aesthetic qualities, corrosion resistance, and symbolic value. It is used for the production of cases, bracelets, external components (dials, hands, etc.), and, more rarely, certain technical parts, including wheel blanks and, in some cases, bridges and mainplates.

In its pure form, gold is highly ductile but has low mechanical strength, which requires it to be used in alloyed form. These alloys not only improve its mechanical properties but also allow its color to be adjusted, resulting in a wide range of standardized shades.

Main Properties

Gold exhibits several remarkable characteristics:

  • Excellent corrosion resistance
  • Very high ductility and malleability
  • Good thermal and electrical conductivity
  • Non-magnetic material
  • Low Young’s modulus (~70–80 GPa)
  • High density (~19.3 g/cm³ for pure gold)

1. Yellow Gold and Rose Gold: Standardized Shades (2N to 5N)

In watchmaking and jewelry, gold colors are defined according to a standardized European scale, generally ranging from 1N to 5N, based on the proportion of copper and silver in the alloy.

👉 The higher the copper content → the redder the color
👉 The higher the silver content → the paler (yellow) the color

Main shades:

  • 2N (light yellow gold)
    Pale yellow tone, rich in silver
    Subtle appearance, slightly greenish
  • 3N (standard yellow gold)
    Balanced tone, the most common in watchmaking
    Good aesthetic compromise
  • 4N (rose gold)
    Pinkish tone, enriched with copper
    Widely used in contemporary watchmaking
  • 5N (red gold)
    Deep red tone
    High copper content

This standardization ensures color consistency between components and across manufacturers.

2. White Gold

Obtained by adding white metals:

  • Palladium (high-end alloys)
  • Nickel (less commonly used today)

Characteristics:

  • Grey-white tone
  • Often coated with rhodium
  • Good mechanical strength

Depending on the nature and content of the alloying element—particularly in nickel-based alloys—white gold may require rhodium plating to achieve a bright, uniform white appearance.

3. Other Variants

  • Grey gold → palladium-based alloys
  • Green gold → gold and silver alloys
  • Black gold → surface treatments or specific alloys

4. Modern Technical Alloys

Some manufactures develop proprietary alloys for specific purposes:

  • Improved scratch resistance
  • Color stability over time
  • Enhanced mechanical properties
  • Marketing differentiation

Gold Fineness

Fineness refers to the proportion of pure gold in an alloy.

  • 24K (999‰) → pure gold
  • 18K (750‰) → 75% gold
  • 14K (585‰) → 58.5% gold

👉 In watchmaking, the standard is 18 carats, offering an optimal balance between purity and mechanical strength. A 22K alloy is also commonly used for the oscillating weights of automatic movements.

Hallmark

A hallmark is an official mark guaranteeing:

  • The fineness of the alloy
  • Its legal compliance
  • Sometimes its origin

Two main types are distinguished:

  • Fineness hallmark → indicates metal purity
  • Maker’s mark → identifies the manufacturer

Gold can be:

Gold is used for:

More rarely:

Advantages

  • Non-tarnishing
  • Prestigious aesthetic
  • Wide range of colors
  • Excellent finishing capability
  • Non-magnetic

Limitations

  • High cost
  • High density
  • Susceptibility to scratching
  • Requires alloying