Prasiolite
From The Gemology Project
| Prasiolite | |
|---|---|
| Chemical composition | SiO2 Silicon dioxide |
| Crystal system | Trigonal |
| Habit | Prismatic |
| Cleavage | Poor |
| Fracture | Conchoidal |
| Hardness | 7 |
| Optic nature | Uniaxial + |
| Refractive index | 1.544 - 1.553 |
| Birefringence | 0.009 |
| Dispersion | 0.013 |
| Specific gravity | 2.63 - 2.65 |
| Lustre | Vitreous |
| Pleochoism | Weak to strong |
Prasiolite is the green variety of quartz.
The color is caused by heat of either natural occuring amethyst (by exposure to sunlight or artificial) or by artificial heat treatment of irradiated amethyst. The former will give a more stable green color that is less prone to fading.
Synonyms: Prasiolita, greened amethyst, green quartz.
Misnomers: Green amethyst.
The name "prasiolite" should not be confused with prasolite (a green variety of the chlorite group) and praseolite which is the green variety of cordierite.
Diagnostics
Chelsea Colour Filter
Reactions under incandescent light:
Irradiated green quartz: red.
Heat treated green quartz: green.
