Amethystine quartz or amethyst varies in color from light to clear-dark
purple, sometimes nearly black, and from light to dark bluish-violet.
The coloring of the stone is supposed to be due to manganese.
The best amethysts come from Brazil and Ceylon, but good specimens are
found in India, Persia, Botany Bay, Transylvania, near Cork and the
island of May in Ireland, at Oberstein, in Saxony, in Hungary, Siberia,
Nova Scotia, Sweden, Bohemia, Canada, and in the States of Maine,
Pennsylvania, Colorado, Georgia, Virginia, and Michigan.
Under heat, the amethyst turns first yellow, then green, and finally
becomes colorless. The value of an amethyst depends upon the fashion,
and the time has been when these stones ranked among the most valuable
of precious stones. At present, a fine amethyst can be bought for very
little money, but should the stone become fashionable again, the best
specimens will command good prices.