Base elements → Materials → Organic materials

MOTHER-OF-PEARL

Table of main properties of mother-of-pearl

 

Property Typical Value Remarks
Density ~2.6–2.8 g/cm³ Moderate
Young’s modulus (E) ~60–80 GPa Moderate
Tensile strength ~100–200 MPa Depends on structure
Hardness (HV) ~200–400 HV Moderate
Hardness (Mohs) ~3.5–4 Relatively low
Thermal conductivity ~2–5 W/m·K Low
Electrical conductivity Very low Insulating material
Thermal expansion ~10–15 ×10⁻⁶ /K Moderate
Melting point Not applicable Decomposes when heated
Magnetism No Non-magnetic
Corrosion resistance Good Sensitive to acids and chemicals
Machinability Limited Fragile, requires careful machining

Mother-of-pearl is an organic material produced by certain mollusks, forming the inner layer of their shells. It is primarily composed of calcium carbonate (aragonite) and organic matter (conchiolin), arranged in a very fine lamellar structure.

In watchmaking, mother-of-pearl is used exclusively for its aesthetic properties, particularly in the production of dials. It is distinguished by its natural iridescent reflections, resulting from light interference within its structure.

Main Properties

Mother-of-pearl exhibits specific characteristics:

  • Low density (~2.6–2.8 g/cm³)
  • Natural lamellar structure
  • Iridescent optical effect (light interference)
  • Non-magnetic material
  • Good chemical resistance
  • Low mechanical strength
  • Sensitivity to shocks and stress

👉 Its value lies primarily in its unique visual appearance.

Mother-of-pearl is composed of:

  • Microscopic aragonite platelets
  • Bound by an organic matrix

This structure gives it:

  • A certain relative resilience (higher than a pure crystal)
  • Overall fragility under mechanical stress
  • An anisotropic behavior

Each piece of mother-of-pearl is unique in terms of:

  • Color
  • Reflections

Mother-of-pearl used in watchmaking mainly comes from:

  • Pearl oysters (Pinctada)
  • Abalone → highly colorful mother-of-pearl

Common types:

  • White mother-of-pearl
  • Grey mother-of-pearl
  • Pink mother-of-pearl
  • Black mother-of-pearl
  • Abalone mother-of-pearl (multicolored)

The main steps are:

  • Cutting of the shell
  • Sawing into thin plates
  • Precision machining (diameter, drilling)
  • Polishing
  • Assembly onto a support (often metallic)

👉 Mother-of-pearl is often bonded to a backing to ensure stability.

👉 In some cases, the backing can be painted to artificially tint the mother-of-pearl.

👉 Although fragile, mother-of-pearl is well suited to engraving and guilloché (engine-turning) work.

1. Dials (Primary Use)

  • Natural mother-of-pearl dials

👉 Unique visual effect, changing with light

2. Decoration

  • Applied indexes
  • Decorative elements

3. Jewelry

  • Combination with precious stones
  • Marquetry

Advantages

  • Unique aesthetic (natural iridescence)
  • Each piece is different
  • Noble and natural material
  • Non-magnetic
  • Good chemical stability

Limitations

  • High fragility
  • Sensitivity to shocks
  • Requires a rigid backing
  • Natural variability (non-homogeneous)
  • Strictly decorative use