Amethyst Gemstones – Properties, Origins, Treatments and Buying Guide

Amethyst is one of the world’s most recognisable and treasured gemstones, admired for its rich purple tones and exceptional clarity. As the most valuable variety of quartz, amethyst has been prized for centuries in jewellery, royal regalia and spiritual objects. Its balance of beauty, durability and affordability makes it one of the most popular gemstones globally.

In this guide we examine amethyst from a professional gemmological and commercial perspective, covering its physical properties, crystal structure, treatments, origins and how to identify fine-quality stones.

Amethyst is the purple variety of quartz, coloured by trace amounts of iron and natural irradiation during crystal formation. It ranges from light lavender to deep royal purple, with the finest stones displaying rich saturation and excellent transparency.

Amethyst crystals typically form in geodes and volcanic cavities, often growing into large, well-defined crystals suitable for both faceted gemstones and ornamental specimens.

Amethyst has the chemical formula:

SiO₂

It is composed primarily of:

Silicon
Oxygen
Trace iron (colouring element)

Natural irradiation alters the iron within the crystal lattice, producing amethyst’s characteristic purple colour. Deeper colour saturation generally increases value.

High-quality amethyst displays strong colour, excellent clarity and even tone distribution.

Amethyst belongs to the quartz mineral family, one of the most abundant and widely distributed mineral groups on Earth.

Its crystal system is trigonal, forming hexagonal prisms that often terminate in well-defined crystal points.

Amethyst offers an excellent balance of brilliance, durability and colour, making it ideal for all types of jewellery.

Lustre
Amethyst has a vitreous (glassy) lustre that gives it a bright, clean appearance.

Transparency
Gem-quality amethyst is transparent, with minimal inclusions.

Refractive index
1.54 – 1.55, providing good brilliance and light return.

Specific gravity
2.65, typical for quartz gemstones.

Amethyst occurs in a wide range of purple shades, including:

Light lavender
Lilac
Violet
Deep royal purple
Reddish-purple

The most valuable stones show deep, even colour with flashes of red or blue under light.

Amethyst has a Mohs hardness of 7, making it suitable for rings, earrings, pendants and bracelets.

While durable, it can still be scratched by harder gemstones and should be protected from heavy impact.

Most amethyst on the market is untreated.

Some stones are heat treated to alter colour, often turning pale amethyst into yellow citrine.
Heat treatment is stable and widely accepted within the gemstone trade.

No coatings or fillings should be present in fine-quality amethyst.

Avoid prolonged exposure to strong heat or direct sunlight.
Clean using warm water, mild soap and a soft brush.
Avoid ultrasonic and steam cleaners.
Store separately from harder gemstones.

Major sources of amethyst include:

Brazil
Uruguay
Zambia
Madagascar
Russia
Namibia

Brazil and Uruguay are particularly renowned for producing deep purple, high-quality stones.