Cubic zirconia

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Cubic zirconia in ring
MFA# 2006.453
Cubic zirconia


A crystal clear, synthetic Diamond Gemstone. Cubic zirconia (CZ) are very hard and have a high refractive index. It is composed of a single crystal of synthetically prepared Zirconium oxide. During manufacture, calcium or yttrium are added as a metal oxide stabilizer, which allows the growth of the single crystal. The technique was first researched in France in the 1960s, then perfected in Russia in 1973 at the Lebedev Physical Institute. Commercial imitation diamonds have been on the market since 1976. Some coatings have been applied in recent years that make the stone visually indistinguishable from diamonds. The variations between the two stones are: 1) CZ are flawless, unlike natural diamonds, and 2) CZ has a lower thermal conductivity, higher dispersion, higher specific gravity, and often a poorer faceted cut.

Synonyms and Related Terms

CZ; cubic zirconium; Matura diamond; imitation diamond; Pink Ice; Fianit (Russian); circonita (Esp.); zircão cúbico (Port.)

Raman spectrum of synthetic cubic zirconia; RRUFF

Physical and Chemical Properties

  • Cubic zirconia has a low thermal conductivity while diamonds have a high thermal conductivity
  • Luster = adamantine
  • Cleavage = none
  • Fracture = conchoidal
  • Fluorescence = often yellow to greenish in SW and yellow to orangish in LW, but not diagnostic
  • Birefringence = none
Mohs Hardness 8.5
Melting Point 2750 C
Density 5.6-6.0 g/ml
Refractive Index 2.15-2.18
Dispersion 0.058-0.066 (strong fire)


Properties of Natural and Simulated Diamonds

Resources and Citations=

  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • Wikipedia: Cubic_zirconia (Accessed Sept. 20, 2005 and Dec 2022)