Russian Origins

The unusual properties of alexandrite caused a lot of confusion upon its discovery. In the first part of the nineteenth century, a Russian nobleman and mineralogist named Lev Alekseyevich von Perovski gifted a sample of a newly mined, unidentified mineral to Finnish researcher Nils Gustaf Nordenskiöld. Nordenskiöld initially thought the greenish gemstone to be emerald, but once the night had fallen and candles were lit up, the alexandrite naturally changed its colour, to the great surprise of the Finn. Sharing the news of his discovery with von Perovski, Nordenskiöld suggested to name the stone ‘diaphanite’ (from Greek ‘di’, meaning ‘two’ or ‘double’; and ‘phan’, ‘to appear’, or ‘seem’); The count however preferred to emphasise the Russian genesis of the discovery thus branding it ‘Alexandrite’, in honour of late tsar Alexander I and his grandson, future tsar Alexander II.

The Alexandrite Effect

Alexandrite is an extremely durable, type-2 gemstone, which indicates a tendency for visible inclusions, especially in larger stones. What differentiates alexandrite from other chrysoberyl varieties is the presence of chromium ions in its crystal structure. The chromium gives the mineral its extraordinary light-absorbing properties, which combined with the physiological response of the human eye result in observable colour changes. This is also called ‘The Alexandrite effect’, a term used to describe similar, colour-changing features of other gemstones, such as sapphires, spinels and garnets. Another characteristic of alexandrite worth noting would be its pleochroism, which is the ability to change colour depending on direction the stone is being viewed from.

How to Make an Alexandrite

The existing deposits of alexandrite are scarce, therefore good-quality, sizeable stones can be very valuable. Natural alexandrite cannot be treated or enhanced in any way; Nevertheless, there are several methods to produce its simulated or synthetic versions. The Czochralski process creates alexandrites that are chemically most accurate, yet fairly easy to identify, as they contain almost no inclusions and have visible growth lines, otherwise known as ‘striae’. By contrast, apparent inclusions in flux-grown minerals will make them indistinguishable to the naked eye. Hydrothermal synthesis will result in gemstones with both physical and chemical properties most closely matching the natural mineral. Lastly, ‘Simulated alexandrite’ is the name given to samples of corundum or spinel laced with trace elements of chromium or vanadium. The properties of these minerals will only partially resemble alexandrite, i.e. the colour change will occur only between purple and pink.