– A –
Amethyst is a variety of Quartz that is transparent and crystalline, usually deep purple to pale bluish-violet; the hues are sometimes mingled in the same stone, owing to irregular colour zoning, and some show patches of yellow. Other colours are reddish-mauve (Siberian stones), reddish-violet (Uruguayan stones) or grey-mauve (Mexican stones).
When natural amethysts (not the variety from Madagascar) are heated, the colour changes to pale yellow (sometimes then mistaken for Citrine, but distinguishable by its dichroism); when the heat is increased, it changes to dark yellow or reddish-brown and, when increased further, to milky white. Some Brazilian amethysts when heated change colour to green.
Specimens containing inclusions of goethite or other fibrous minerals are polished as cats eye’s. Amethysts have been set in globular or pear-shaped pendants and as pierced beads for necklaces and ear-drops. Some large stones have been embellished by having set into them a design of small diamonds.