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Chemical composition Silicon dioxide SiO2
Crystal system Trigonal
Habit Prismatic
Cleavage Poor
Fracture Conchoidal
Hardness 7
Optic nature Uniaxial +
Refractive index 1.544 - 1.553
Birefringence 0.009
Dispersion Low, 0.013
Specific gravity 2.63 - 2.65
Lustre Vitreous
Pleochroism Weak to distinct
Citrine oval faceted on Madiera Citrine Crystals.
Photo courtesy of Barbra Voltaire

Citrine is a yellow or golden variety of quartz. Most citrine available today is heat-treated amethyst. When amethyst is heated to about 482.2 degrees Celsius, it alters to to a golden tone. Citrine has been credited with curing urinary tract infections, jaundice and kidney ailments. This is obviously a color association.

Inclusion Images: Click on Image for Full Size

Citrine showing color banding.This stone was originally an amethyst which was heat treated.
Photo courtesy of Conny Forsberg