Amethysts are the purple variety of quartz crystal. They have been prized for many centuries for their rich colour and were used for beads, seals and other ornaments. In the late 18th and early 19thC amethysts were mainly used for ecclesiastical jewellery or by royalty, because they were very expensive at that time. During the 1850s large deposits were discovered in Brazil, making the mining of amethysts easy – their price plummeted and never recovered. The Stone ceased to be rare and became widely used. Large amethysts can still be bought relatively inexpensively.

Colour

Colour is the most important factor in determining the value of an amethyst. A good’ stone should be a deep, rich velvety purple with a soft appearance. Due to their naturally irregular colour zoning, it is fairly unusual to find a perfectly evenly coloured stone. This can be seen in the faceted stones where the colour fades at the top. Siberian amethysts, considered to be the best, tend to be a soft reddish mauve. Uruguayan examples are more violet in hue, and Mexican stones are a paler greyish mauve.

Clarity

Clarity is also a factor in the quality of an amethyst: generally only the clearest stones are faceted. The stones heavily flawed, has been polished as a cabochon to play down these flaws. The grading of amethysts, unlike many gemstones, is based not on inclusions but on visual effect.