Basically, citrine is heat treated Amethyst. You can often see elongated parti-colored stones where one end has been heated.
The process is relatively simple. At 470 degrees C., amethyst turns light yellow. At 550 - 560 C, the material becomes dark yellow to reddish brown. Smoky quartz can turn yellow at 300 - 400 C.
Properties
- Crystal System - Hexagonal (Trigonal)
- Hardness - 7
- Specific Gravity - 2.65
- Refraction - Double
- Refractive Index - 1.54 to 1.55
- Dispersion - .013
- Birefringence - .009
- Wearability - Very Good
- Special Care - None