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Ever since the advent of the synthetic material cubic zirconia, natural zircon has been sadly and wrongfully associated with it.  Zircon is in no way related to cubic zirconia apart from their similar sounding names and because of this, zircon is a generally under-rated gemstone.  It is a very bright and lively gemstone with high dispersion and diamond like lustre.  It is the birthstone of December and is available in a range of colours including vivid electric blues, greens, yellows, oranges, brown to reds and colourless stones.  The predominant countries where zircon is mined are: Cambodia, Thailand, Sri Lanka, Myanmar (Burma) and Australia.    

Zircon (High Type)
Mohs’ Hardness: 6.5-7.5
Specific Gravity: 4.60-4.80
Refractive Index: 1.900-2.010
Treatments: Heating
Incidence: Always (For blue and colourless varieties)
Purpose: To produce colourless and blue colours
Durability: Fair to good
Special Care: None
Synthetics: None
Possible Imitations: CZ

Zircon (Intermediate Type)
Mohs’ Hardness: 6.5-7.5
Specific Gravity: 4.10-4.60
Refractive Index: 1.783-1.950
Birefringence: 0.008-0.043
Optic Sign & Character: Uniaxial Positive

Zircon (Low Type)
Mohs’ Hardness: 6.5-7.5
Specific Gravity: 3.90-4.10
Refractive Index: 1.780-1.815
Optic Sign & Character: Isotropic