Alexandrite is named after the Russian tsar Alexander II (1818-1881), the very first crystals having been discovered in April 1834 in the emerald mines near the Tokovaya River in the Urals. The discovery was made on the day the future tsar came of age. Although alexandrite is a relatively young gemstone, it certainly has a noble history. Since it shows both red and green, the principal colours of old Imperial Russia, it inevitably became the national stone of tsarist Russia.Beautiful alexandrite in top quality, however, is very rare indeed and hardly ever used in modern jewellery. In antique Russian jewellery you may come across it with a little luck, since Russian master jewellers loved this stone. Tiffany’s master gemologist George Frederick Kunz (1856-1932) was also fascinated by alexandrite, and the jeweller’s firm produced some beautiful series of rings and platinum ensembles at the end of the 19th and beginning of the 20th century. Smaller alexandrites were occasionally also used in Victorian jewellery from England.
Alexandrite is the rare colour-change variety of the mineral chrysoberyl . Its rarity is a result of its unlikely chemical makeup. Alexandrite can only form when aluminium and beryllium combine with trace elements like iron, titanium and, most importantly, chromium. On rare occasion, vanadium may also be present. The unlikelihood of the rare element chromium being in the right place to combine with aluminium and beryllium under exactly the right conditions to create alexandrite is what makes it so rare and valuable
The magic of converting colorations.
The most sensational characteristic approximately this stone, however, is its unexpected potential to exchange its coloration. Green or bluish-inexperienced in sunlight hours, alexandrite turns a tender colour of pink, purplish-red or raspberry red in incandescent mild. This specific optical characteristic makes it one of the maximum treasured gemstones of all, particularly in nice qualities.
Alexandrite is very scarce: this is due to its chemical composition. It is basically a chrysoberyl , a mineral consisting of colourless or yellow transparent chrysoberyl , chrysoberyl cat’s eye and colour-changing alexandrite (also in cat’s eye varieties). It differs from other chrysoberyl s in that it not only contains iron and titanium, but also chromium as a major impurity. And it is this very element which accounts for the spectacular colour change. Rarely, vanadium may also play a part. According to CIBJO nomenclature, only chrysoberyl s displaying a distinct change of colour may be termed alexandrite.
Like many other gemstones, alexandrite emerged millions of years ago in a metamorphic environment. But unlike many others, its formation required specific geological conditions. The chemical elements beryllium (a major constituent in chrysoberyl ) and chromium (the colouring agent in alexandrite) have contrasting chemical characteristics and do not as a rule occur together, usually being found in contrasting rock types. Not only has Nature brought these contrasting rock types into contact with each other, but a lack of the chemical element silica (the second most common element in the Earth's crust) is also required to prevent the growth of emerald. This geological scenario has occurred only rarely in the Earth's history and, as a result, alexandrite crystals are very scarce indeed.
Russia has remained the number one source of alexandrite given that gemstones from the mines of the Urals became to be had available on the market. When the Russian deposits have been thought to have been exhausted, interest inside the precise shade miracle decreased - mainly considering that alexandrites from other mines not often displayed the coveted colour alternate. But the scenario modified dramatically in 1987, when alexandrites had been observed in an area referred to as Hematita in Minas Gerais, Brazil. The Brazilian alexandrites showed each a extraordinary color exchange and properly readability and coloration. Thus the really dulled image of the wonderful stone acquired some other raise. The colour of the Brazilian stones is absolutely now not as robust a green as that of Russian alexandrite, but the coloration exchange is clearly discernible. Today Hematita is one of the most critical deposits of alexandrite in financial terms. Occasionally alexandrite with chatoyancy is observed there, an effect which has not yet been located in Russian alexandrite. Alexandrites also are acquired from resources in Sri Lanka, but the hue of those stones compares much less than favourably with that of the Uralian alexandrites. They seem inexperienced in daytime and a brownish pink in synthetic light. The Tunduru area in southern Tanzania has also produced some extraordinary specimens for the reason that mid-1990s. Alexandrites are also located in India, Burma, Madagascar and Zimbabwe. Although this stone is still considered a rarity, specialised gemstone dealers do stock it, specially considering the fact that progressed change relationships among Russia and the rest of the sector have ensured a higher supply of Russian alexandrites to the marketplace.
|Colour||Blue, Red, Green, Yellow, Pink, Purple, Gray, Multicolored|
|Refractive Index||1.744 - 1.755|
|SG||3.5 - 3.8|
|Transparency||Transparent to nearly opaque|
|Cleavage||1,1 ; 3,2. Often exhibits parting along twinned crystals.|