Zircon
Zircon is a beautiful gem when properly cut because its dispersion is very high, close to a Diamond’s. The chemical formula of Zircon is ZrSiO4 and its molecular weight is 190.31 gm. Zircon is found in a variety of colors including blue, green, yellow, red, brown and colorless. Blue is the most popular color and can only be produced by heating reddish-brown crystals. Green Zircon may be slightly radioactive if it contains Uranium or Thorium. Zircon has a specific gravity of 4.60 – 4.70 (g/cm3) and the refractive index of 1.925 – 2.015 Uniaxial ( + ); Isotropic when metamict.
Zircon is often confused with the artificial diamond simulant Cubic Zirconia. Cubic Zirconia’s formula is ZrO2 (zirconium oxide) and Zircon is ZrSiO4 (zirconium silicate). Zircon has also been used as a diamond simulant and resembles Diamond in luster and fire. Colorless Zircon may even be mistaken for a Diamond by experienced jewelers. Zircon is an attractive and affordable gemstone and is the December birthstone.
Zircon is a very widely distributed mineral, but fine crystals are relatively rare.
| Category: | Nesosilicates |
| Chemical Formula: | ZrSiO4 |
| Molecular Weight: | 190.31 gm |
| Crystallography: | Tetragonal – Ditetragonal Dipyramidal |
| Crystal Habit: | Most commonly as tabular to prismatic crystals, with square cross sections, terminated by [111], to 30 cm; as irregular grains, massive. |
| Twinning: | On [101], geniculated. |
| Composition: | La,Ce,Pr,Nd,Sm, | 3.78 % | RE | 4.41 % | REE2O3 |
| Hafnium | 4.69 % | Hf | 5.53 % | HfO2 | |
| Zirconium | 43.14 % | Zr | 58.27 % | ZrO2 | |
| Silicon | 14.76 % | Si | 31.57 % | SiO2 | |
| Oxygen | 33.63 % | O | |||
| 100.00% | 99.79% | =TOTAL OXIDE |
| Cleavage: | [110] Indistinct, [111] Indistinct |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Hardness (Mohs): | 7.5 |
| Density: | 4.60 – 4.70 (g/cm3) |
| Luminescence: | Yellow in SW UV, dull red in LW UV. Thermoluminescent. Cathodoluminescent. |
| Radioactivity: | Not normally Radioactive (Radioactive when metamict; when it contains Uranium or Thorium) |
| Color: | Reddish Brown, Yellow, Green, Blue, Gray, Colorless |
| Transparency: | Transparent to Translucent to Opaque |
| Luster: | Vitreous to Adamantine; Greasy when metamict |
| Refractive Index: | 1.925 – 2.015 Uniaxial ( + ); Isotropic when metamict |
| Birefringence: | 0.055 |
| Dispersion: | Very Strong |
| Pleochroism: | Very Weak |
