MENU
1. Table of Sapphire’s Main Properties
| Property | Typical Value | Remarks |
|---|---|---|
| Density | ~4.0 g/cm³ | Close to ruby |
| Modulus of Elasticity (E) | ~350–400 GPa | Very high |
| Tensile strength | Low | Brittle |
| Hardness (HV) | ~2000 HV | Very high |
| Hardness (Mohs) | 9 | Identical to ruby |
| Thermal conductivity | ~25–40 W/m·K | Medium |
| Electrical conductivity | None | Insulator |
| Expansion coefficient | ~5–8 ×10⁻⁶ /K | Low |
| Magnetism | No | Non-magnetic |
| Corrosion resistance | Excellent | Inert |
| Machinability | Very difficult | Diamond tools |
2. General description
Sapphire is, like the Ruby / Jewel, a variety of corundum (Al₂O₃). It differs from ruby only by the absence of chromium, which gives it transparency or various shades. In watchmaking, it is used in two distinct forms:
- Natural Sapphire → mainly in jewelry (Setting (stone/jewel setting))
- Synthetic Sapphire → widely used for crystals, cases and technical components (discs, bearings, pushers)
Today, synthetic Sapphire has become an essential Material due to its transparency, Hardness, and scratch resistance.
3. Natural Sapphire and Synthetic Sapphire
Natural Sapphire
Natural Sapphire is extracted from mineral deposits.
Characteristics:
- Color variability (blue, yellow, pink, etc.)
- Natural inclusions
- Primarily used in jewelry
Applications:
- Jewelry
- Setting (stone/jewel setting) cases, bracelets, dials etc.
Synthetic Sapphire
Synthetic Sapphire is industrially produced from Aluminium oxide.
Main methods:
- Verneuil process (flame fusion)
- Czochralski growth
- Kyropoulos (widely used for large pieces)
Characteristics:
- High purity
- Perfect transparency (or controlled colors)
- Constant properties
- Controlled production
👉 It is now the standard in watchmaking.
4. Manufacturing of Sapphire components
The main steps are:
- Crystal growth
- Cutting into blocks or wafers
- Machining (diamond tools)
- Optical Polishing
- Treatments (anti-reflective, etc.)
👉 Machining is long and costly due to the Hardness of the Material.
5. Watchmaking Applications
Watch crystals (synthetic Sapphire)
- Main application
- Scratch resistance
- High transparency
Often treated with an anti-reflective coating.
Sapphire cases (synthetic Sapphire)
- Cases that are fully transparent (or colored and translucent)
👉 Allow the Movement from all angles
Jewelry (natural sapphire)
- Set natural sapphires
- Decorative elements
6. Advantages and limitations
Advantages
- Very high scratch resistance
- Exceptional transparency
- Chemical stability
- Non-magnetic
- High-end aesthetics
- Durability
Limitations
- Fragility (brittle)
- Sensitivity to impact
- Difficult and costly machining
- Not completely scratch-resistant (Diamond only higher)
This page was automatically translated from the French reference version using an artificial intelligence tool. Errors or inaccuracies may remain. If you notice any, especially if this is your native language, please feel free to report them to info@horopedia.org. Your contribution helps us improve the quality of the encyclopedia.
Until translated, images and videos will temporarily remain displayed in French.
Thank you for your understanding.