Amethyst

Overview

Amethyst is the purple variety of quartz. Its colour comes from iron combined with natural irradiation in the earth. Once counted among the most precious gems, it became affordable after large deposits were found in South America, yet fine, deeply coloured amethyst is still a beautiful and durable choice.

Colour

The most valued amethyst is a strong reddish purple to purple without being so dark that it looks black in dim light. Colour zoning (bands of lighter and darker purple) is common and lowers value when visible face-up. Trade names such as "Siberian" describe a colour grade (deep purple with red and blue flashes), not necessarily an origin.

Key properties

Where amethyst comes from

Brazil and Uruguay produce large quantities, often from geodes. Zambia is known for deeply coloured stones with a slightly bluish purple. Bolivia (where amethyst and citrine occur together as ametrine), Madagascar, Mexico and Russia's Ural mountains are other sources.

Treatments

Most amethyst is not treated. Heating can lighten stones that are too dark, and at higher temperatures turns many amethysts yellow to orange: much of the citrine on the market was made this way. Synthetic amethyst exists and is hard to separate from natural without laboratory testing.

Buying tips

• Look for even colour with no obvious lighter bands when you look straight down through the table.
• Eye-clean is the standard for faceted amethyst; visible inclusions should be reflected in the price.
• Ask whether a high-value stone has been tested to confirm it is natural.

Care and cleaning

Clean with warm soapy water and a soft brush. Ultrasonic cleaners are usually safe for untreated stones without fractures; avoid steam and heat. Some amethyst can fade after long exposure to strong light, so do not leave it in a sunny window.