Alexandrite – the colour-changing variety of chrysoberyl
Appearance & Properties
Alexandrite is the colour-changing variety of chrysoberyl, a beryllium aluminium oxide with the formula BeAl₂O₄. In daylight it commonly appears green, bluish green or olive green; under incandescent or candlelight it may shift towards red, purplish red or raspberry tones. The effect is caused mainly by chromium and is an optical response to the light source, not a coating or surface illusion. Alexandrite is usually transparent to translucent and may also show strong pleochroism, meaning different colours are seen in different crystal directions. It ranks 8.5 on the Mohs scale, making it a durable jewellery stone, although inclusions, fractures and sharp edges still require care.
History & Discovery
Alexandrite was recognised or discovered in the Russian Urals around 1830, in the Tokovaya area near Ekaterinburg. Historical accounts differ about the precise discovery and naming sequence. The discovery is often associated with the Finnish mineralogist Nils Gustaf Nordenskiöld, while the name is commonly linked to Count Lev Alekseevich Perovskii. It was named for the future Tsar Alexander II. Exact dates and details, including the connection with his coming-of-age in 1834, vary among accounts. The stone’s green-and-red appearance was especially appealing in Imperial Russia, since those colours echoed the national military colours of the period. For many decades the Urals supplied the finest material, but production later declined. New deposits, particularly in Brazil, helped re-establish alexandrite as an internationally important gem.
Occurrences
The historic source is the Tokovaya district in Russia’s Sverdlovsk region, where fine crystals were found in emerald-bearing rocks. Production there is now limited compared with the nineteenth century. Important later sources include Brazil, especially the states of Minas Gerais and Bahia; some Brazilian stones show a strong and attractive colour change. Alexandrite has also been reported from Sri Lanka, Tanzania, India, Madagascar and Zimbabwe, among other localities. Material differs considerably from one deposit to another in colour, transparency, size and the strength of its change. A locality is therefore not proof of quality. The presence of an origin claim for any individual gem should be supported by appropriate documentation, and should not be assumed from appearance alone.
Famous Examples & Interesting Facts
A well-known institutional example is the 65.7-carat alexandrite in the Smithsonian National Gem Collection in Washington, D.C., often cited among the notable large faceted stones on public display. Alexandrite cat’s-eye is another highly prized form: aligned needle-like inclusions can create a bright moving band across a cabochon, combining colour change with chatoyancy. The most useful identification clue is the change between different types of light, but colour alone is not conclusive. Modern laboratory-created alexandrite can closely reproduce the chemistry and optical behaviour of natural material. Some colour-changing stones sold under misleading names are actually synthetic corundum or other imitations, so reliable identification requires gemmological testing.
Jewellery & Use
Alexandrite is suitable for rings, earrings, pendants and bracelets, and it is commonly fashioned as an oval, cushion, round or mixed cut. Faceting helps display its colour change, while cabochon cutting is preferred for cat’s-eye material. Its hardness of 8.5 and lack of a pronounced cleavage make it reasonably resistant to everyday wear, but inclusions or fractures can reduce toughness. Protect it from severe knocks, sudden temperature changes and prolonged contact with harsh chemicals. Warm water, mild soap and a soft brush are generally appropriate for cleaning. Steam or ultrasonic cleaning should be avoided when a stone contains significant fractures or inclusions. Natural, laboratory-created and imitation materials should be clearly distinguished; treatments, if present, depend on the individual stone.
Symbolism, Astrology & Tradition
Alexandrite is often described in modern jewellery writing as a symbol of transformation, adaptability and duality because its colour changes with the light. These are symbolic associations, not scientific properties. It is sometimes promoted as a June birthstone alongside pearl and moonstone, although birthstone lists vary by country and organisation. Some contemporary astrology traditions associate it with Gemini or with planetary themes of change; these are beliefs rather than established gemmological facts. Russian historical tradition gave the stone patriotic significance through its green-and-red colours and connection with Alexander II. Modern crystal and esoteric traditions may attribute emotional or spiritual benefits to alexandrite, but such claims are folklore or personal belief and have not been demonstrated scientifically. It has no proven medical effect.