Difference between revisions of "Zircon"

From The Gemology Project
Jump to: navigation, search
 
Line 1: Line 1:
 
{{zircon}}
 
{{zircon}}
 +
 +
Zircon is a mineral species, that can be broadly defined as a zirconium silicate containing trace amounts of the radioactive minerals hafnium, uranium and thorium. Over time, these radioactive components break down the lattice of the crystal, eventually (over tens of thousands of years) destroying the crystal, leaving it with an amorphous structure and a dark pithy appearance. Zircons that are young and unaffected by radioactivity are termed "high" zircons. These stones are transparent golden, yellowish-green and greenish-brown in color with incredibly high dispersion. "High" zircons can be heated to temperatures greater than 1800 degrees Fahrenheit and become colorless or blue. These highly dispersive colorless stones have long been used as diamond substitutes. That's why the name zircon has the connotation of synthetic or imitation. It was used to imitate a diamond, but the stone is indeed naturally occurring. It should not be confused with the synthetic cubic zirconium (zirconia), which is in no way related to zircon.

Revision as of 13:12, 2 October 2006

Zircon
Chemical composition ZrSiO4 Zirconium silicate
Crystal system Tetragonal
Habit Prismatic (squared) with pyramidal terminations
Cleavage Poor
Hardness 7.5
Optic nature Uniaxial + to isotropic
Refractive index 1.78 - 1.99
Birefringence Up to 0.059
Dispersion High, 0.039
Specific gravity 3.90-4.69
Lustre Vitreous to sub-adamantine
Pleochroism Weak (stronger in heat-treated)

Zircon is a mineral species, that can be broadly defined as a zirconium silicate containing trace amounts of the radioactive minerals hafnium, uranium and thorium. Over time, these radioactive components break down the lattice of the crystal, eventually (over tens of thousands of years) destroying the crystal, leaving it with an amorphous structure and a dark pithy appearance. Zircons that are young and unaffected by radioactivity are termed "high" zircons. These stones are transparent golden, yellowish-green and greenish-brown in color with incredibly high dispersion. "High" zircons can be heated to temperatures greater than 1800 degrees Fahrenheit and become colorless or blue. These highly dispersive colorless stones have long been used as diamond substitutes. That's why the name zircon has the connotation of synthetic or imitation. It was used to imitate a diamond, but the stone is indeed naturally occurring. It should not be confused with the synthetic cubic zirconium (zirconia), which is in no way related to zircon.