In the 20th century, the color of amethyst was attributed to the presence of manganese. However, since it is capable of being greatly altered and even diacharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate was suggested, and sulfur was said to have been detected in the mineral.
More recent work has shown that anethysts’ coloration is due t ferric iron impurities. Further study has shown a complex interplay of iron and aluminium is responsible for the color.
On exposure to heat, anethyst generally becomes yellow, and much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely “burnt amethyst”. Veins of amethystine quartz are apt to lose their color on the exposed outcrop.
This horseshoe charm is made with 12 carat weight cabochon amethyst, 0.08 weight carat square emeralds, 0.18 carat weight round brilliant diamonds and platinum and comes from Tiffany Charms. It is $1,550.