Ametrine Gemstones – Properties, Origins, Treatments and Buying Guide

Ametrine is a rare and captivating gemstone, combining the rich purple of amethyst with the golden yellow of citrine in a single crystal. Its unique colour zoning makes each stone one-of-a-kind and highly prized among collectors and jewellery designers.

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

Ametrine is a naturally occurring variety of quartz that exhibits both amethyst and citrine colours in the same crystal. The colour zoning results from differing oxidation states of iron within the crystal during formation. Ametrine is found in quartz veins and hydrothermal deposits, often forming large crystals suitable for faceting.

Ametrine has the chemical formula:

SiO₂

This means it is composed primarily of:

Silicon
Oxygen

The unique combination of purple and yellow colours is caused by natural iron impurities within the quartz lattice and exposure to varying temperatures during crystal growth.

Ametrine belongs to the quartz mineral family, part of the silicate group.

Its crystal system is trigonal, producing prismatic hexagonal crystals with excellent clarity and the ability to display dramatic colour zoning.

Ametrine combines clarity, brilliance, and unique bi-colour zoning, making it ideal for statement jewellery pieces and collectors.

Lustre
Vitreous, producing a bright and reflective surface.

Transparency
Transparent to very clear; gem-quality stones allow light to pass freely through both colour zones.

Refractive index
1.544 – 1.553, giving good brilliance typical of quartz.

Specific gravity
2.65 – 2.66, standard for quartz.

Ametrine displays a distinctive bi-colour pattern:

Purple (amethyst zone)
Golden yellow (citrine zone)
Orange blends in transitional areas

The most valuable stones have sharp, well-defined colour separation with strong saturation.

Ametrine has a Mohs hardness of 7, suitable for rings, pendants, and earrings. Care is needed to prevent scratches or impact damage due to the brittleness of quartz.

Most ametrine is untreated. Occasionally, heat treatment may be applied to improve colour balance, but high-quality specimens naturally display strong dual colour zones.

Avoid ultrasonic or steam cleaning.
Use warm water, mild soap, and a soft brush.
Store separately from harder stones to avoid scratches.
Protect from strong impact to preserve colour zoning.

Major sources of ametrine include:

Bolivia (Anahi Mine – world’s main source)
Smaller deposits:
Brazil
India
Madagascar