Q12: What's Differences Between Synthetic Corundum and Zircon?
1. Chemical Composition
- Synthetic Corundum:
Composed of aluminum oxide (Al₂O₃). It is chemically identical to natural sapphires and rubies, with trace elements (e.g., chromium for red, iron/titanium for blue) determining color.
- Zircon (Natural):
Composed of zirconium silicate (ZrSiO₄). A distinct mineral with no chemical relation to corundum.
- Cubic Zirconia (Synthetic Zirconia, CZ):
Often confused with zircon; composed of zirconium dioxide (ZrO₂), a lab-created simulant.
2. Hardness (Mohs Scale)
- Synthetic Corundum: 9
Second only to diamond; extremely scratch-resistant and durable.
- Zircon: 6–7.5
Lower hardness, more prone to scratching and wear over time.
- Cubic Zirconia: 8–8.5
Harder than zircon but softer than corundum.
3. Density & Specific Gravity
- Synthetic Corundum: ~3.97–4.1 g/cm³
- Zircon: ~3.9–4.8 g/cm³ (highly variable)
- Cubic Zirconia: ~5.6–6.0 g/cm³
Noticeably heavier than both corundum and zircon.
4. Optical Properties
- Synthetic Corundum:
- Refractive Index: ~1.76–1.78
- Dispersion: Low (0.018)
- Luster: Vitreous (glass-like). Brilliance is subtle and internal.
- Zircon:
- Refractive Index: ~1.78–1.98
- Dispersion: Moderate (0.04)
- Strong birefringence (doubling of facet edges visible under magnification).
- Cubic Zirconia:
- Refractive Index: ~2.15–2.18
- Dispersion: Very High (0.060)
- Excessive "rainbow" fire, often appearing overly brilliant or "glassy".
5. Crystal Structure
- Synthetic Corundum: Hexagonal (trigonal) system.
- Zircon: Tetragonal system.
- Cubic Zirconia: Isometric (cubic) system.
6. Origin & Production
- Synthetic Corundum:
Grown in labs via flame fusion, flux, or hydrothermal methods. Created since the early 1900s.
- Zircon:
A natural mineral formed in igneous rocks, mined from natural deposits.
- Cubic Zirconia:
Mass-produced in labs since the 1970s; no natural equivalent.
7. Common Uses
- Synthetic Corundum:
Jewelry (lab sapphires/rubies), watch bearings, mechanical components, lasers.
- Zircon:
Affordable jewelry, diamond simulants, and collector's stones.
- Cubic Zirconia:
Inexpensive fashion jewelry, diamond simulant.
