Natural Alexandrite – the colour-changing variety of chrysoberyl
Appearance & Properties
Alexandrite is the colour-changing variety of chrysoberyl, a beryllium aluminium oxide with the chemical formula BeAl₂O₄. In daylight it commonly appears green, bluish green or occasionally yellowish green; under incandescent light it may shift to purplish red, raspberry red or brownish red. The effect is caused by chromium and by the different spectral balance of the light source, not by a surface coating. Alexandrite is usually transparent to translucent and may show pleochroism, meaning different colours from different viewing directions. Rare cabochons can display a cat’s-eye band. With a Mohs hardness of 8.5, it is durable, although inclusions, fractures and sharp corners still require care.
History & Discovery
Alexandrite was recognised in the Russian Urals around 1830 or in the early 1830s, in the emerald-bearing region near the Tokovaya River. Historical accounts differ on the precise circumstances and date by which it became known in St Petersburg. Its name is generally understood to honour the future Tsar Alexander II. Its red-and-green colour range also suited imperial Russian symbolism. For many decades, the Urals were the classic source of fine material. Later discoveries in Brazil and elsewhere renewed attention to the gem, although stones with a strong, attractive colour change remain uncommon.
Occurrences
The historic Russian deposits lie in the central Urals, especially around the Tokovaya area, but production there is now very limited. Important later sources include Minas Gerais in Brazil, where notable material was found from the 1980s onward. Alexandrite has also been reported from Sri Lanka, Tanzania, India, Madagascar and Zimbabwe. Material from different localities can vary greatly in body colour, transparency and strength of colour change. A locality list describes known geological sources only; it does not establish the origin of any individual gemstone.
Famous Examples & Interesting Facts
Alexandrite is closely associated with the Russian imperial period because its discovery and name coincided with the rise of Alexander II. Rather than relying on uncertain stories about a single celebrated stone, it is more useful to remember two established facts. First, the colour change is normally strongest when the daylight is relatively blue-green and the artificial light is rich in red wavelengths. Second, alexandrite is not a form of emerald: both can contain chromium, but alexandrite is chrysoberyl, with a different crystal structure and chemical composition. Fine stones are judged especially by the quality of their colour change, transparency and colour balance.
Jewellery & Use
Alexandrite is suitable for rings, earrings, pendants and other jewellery, and it can be faceted in rounds, ovals, cushions or mixed cuts. Faceting emphasises brilliance and colour change; cabochons may be chosen for a cat’s-eye effect. Its 8.5 hardness gives good everyday durability, but strong blows can damage included stones or thin points. Clean it with lukewarm water, mild soap and a soft brush, then rinse and dry carefully. Avoid sudden temperature changes, harsh chemicals and ultrasonic or steam cleaning unless a professional has confirmed that the particular stone is suitable. Natural, synthetic and treated materials should be identified separately.
Symbolism, Astrology & Tradition
In modern jewellery tradition, alexandrite is often listed as a birthstone for June, alongside pearl and moonstone, although birthstone lists vary by country and organisation. It is also sometimes linked with Gemini in contemporary zodiac or crystal traditions. These associations are symbolic or folkloric, not scientific findings. Because of its green-to-red change, alexandrite has been interpreted as a symbol of transformation, balance, adaptability and the meeting of opposites. Russian historical associations have added ideas of imperial prestige. Claims that it heals illness or produces dependable psychological, spiritual or astrological effects belong to esoteric belief and should not be treated as medical fact.