Amethyst (Rough Form)
A semiprecious stone available in color from light violet to dark
purple.The chemical name for Amethyst, Silicon Dioxide (SiO2), along
with distinctive attributes relating to it's color are representative
of its chemical composition. As mentioned through it's physical
properties, Amethyst obtains it's color through a combination of
manganese impurities (Mn) and the existence of iron (Fe) in specific
quantities. The color of each crystal is dependant upon the
distribution of color-filled bands within it. These color bands are
stable only at temperatures below 480 degrees Fahrenheit (248.9
degrees Celsius) so this semi-precious stone should be protected from
extreme heat in order to prevent fading. Professional heating
treatments (on the other hand) have been used on Amethyst to produce
the popular gems known as Citrine and Ametrine (400 and 500 degrees
Celsius). Many of the naturally occurring Citrines began as Amethyst
and were created by being heated by exposure to lava and magma from
nearby volcanoes and other magma containing bodies. Ametrine has
become a popular semi-precious gem which is a product of being half
Amethyst and half Citrine.
Other Characteristics of Amethyst
Index of refraction: 1.5-1.6
Birefringence: 0.01
Mohs' Scale Hardness: 7
Fracture: Conchoidal
Specific Gravity: 6.5
Crystal System: Tetrahedral