Labradorite Gemstones – Properties, Origins, Treatments and Buying Guide

Labradorite is a highly mystical and visually striking gemstone, celebrated for its unique play of colour, known as labradorescence. Unlike brightly coloured stones that rely on saturation, labradorite captivates with flashes of blue, green, gold, and sometimes red or violet when viewed from different angles.

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

Labradorite is a feldspar mineral belonging to the plagioclase series. It forms in igneous rocks, particularly basalt and gabbro, and occasionally in metamorphic rocks. Its hallmark optical effect, labradorescence, is caused by light diffraction within thin layers of the mineral.

Labradorite crystals typically form tabular or blocky shapes with excellent cleavage planes, and gem-quality stones are cut to maximise their colour flash and iridescence.

Labradorite has the chemical formula:

(Na,Ca)(Si,Al)₄O₈

This means it is composed primarily of:

Sodium
Calcium
Aluminium
Silicon
Oxygen

The precise ratio of sodium to calcium affects its optical properties and the intensity of labradorescence.

Labradorite belongs to the feldspar mineral family.

Its crystal system is triclinic, producing blocky or tabular crystals with excellent cleavage planes, which influence both cutting and durability.

Labradorite is prized for its optical effect, labradorescence, which produces vibrant flashes of colour. It also exhibits good transparency in thin slices and moderate brilliance, making it a captivating gemstone for jewellery and collectors.

Lustre
Vitreous to pearly, especially along cleavage planes.

Transparency
Transparent to translucent, thin stones show the best colour flash.

Refractive index
1.560 – 1.572, showing moderate brilliance and strong optical effects.

Specific gravity
2.68 – 2.72, typical for feldspar minerals.

Labradorite displays a fascinating range of colours:

Blue
Green
Gold
Orange
Red
Occasionally violet

Colour flashes shift depending on the viewing angle, creating a dramatic play-of-colour effect.

Labradorite has a Mohs hardness of 6 to 6.5, making it suitable for pendants, earrings, and occasional wear rings.

It has perfect cleavage in one direction and can chip if struck sharply.

Most labradorite is untreated. Occasionally, heat treatment may enhance the labradorescence, but this is rare in high-quality specimens.

Avoid ultrasonic or steam cleaners.
Do not expose to sudden temperature changes.
Clean with warm water, mild soap, and a soft brush.
Store labradorite separately from harder stones to prevent scratches.

Major sources of labradorite include:

Canada (Labrador, Québec)
Madagascar
Finland (Spectrolite)
Russia
Norway