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The Colour changing stone - Alexandrite

Our latest tiktok explores the fascinating colour changing stone, that is Alexandrite, however we've also created this blog which delves a little deeper into the stone.


Prince Alexander II of Russia

History


Alexandrite deposits were first discovered in 1830 near the Tokovaya river in Russia’s Ural Mountains. This first discovery of alexandrite was also on Prince Alexander II of Russia’s birthday, hence the name! Those first alexandrite's were of very fine quality and displayed vivid hues and dramatic colour change. It caught the country’s attention because its red and green colours mirrored the national military colours of imperial Russia.


George Frederick Kunz, the master gemmologist at Tiffany & Co. bought alexandrite reserves so large that it cornered the market on the stone for decades. He also produced a series of alexandrite rings between the late 19th and early 20th centuries. Alexandrite was occasionally used for jewellery in Victorian England as well.


For much of the 20th Century, there were no new discoveries of the mineral and Russia’s gem mines were quickly exhausted, so it became very rare until new supplies were discovered in Brazil in 1987. Brazil, Sri Lanka, and East Africa are now the main sources for alexandrite, though these gems are not as vividly coloured as the original Russian gemstones.

Map of Alexandrite Sources

Natural alexandrite gemstones are now rarer than diamonds. Because it’s so scarcely available, fine-quality alexandrite is practically unaffordable to the general public. Even lower quality stones are expensive and limited in supply.


Stone Characteristics


Alexandrite is part of the chrysoberyl family, which is separate to beryls, being a beryllium aluminium oxide as opposed to a silicate. Chrysoberyls have good durability and a hardness of 8.5 on the Mohs scale, making them perfect for use in jewellery.


The most prized colour change is a strong raspberry red in incandescent light and a bright green in daylight. The colours seen in alexandrite are caused by chromium – the same colouring element that causes the red of ruby and the green of emerald. The amount of colour change observed is often given as a percentage - with a 100% colour change from one hue to the other being the most valuable.


The colour change effect is due to alexandrite transmitting green and red light equally. Incandescent and daylight light sources are richer in different wavelengths (red or blue and green respectively) and this has a direct effect on what colour the gemstone appears to the human eye.



Alexandrite synthetics


Alexandrite has such extreme rarity that those seen on the market might not be quite what they seem. Alexandrite

has been successfully synthesised in laboratories since the 1960s and these synthetics have the same chemical, physical and optical properties of natural alexandrite and show a strong colour change.


However many of these simulants are actually synthetic colour change sapphires, which are cheaper to produce and show a more distinct colour shift.




Caring for your Alexandrite jewellery


Alexandrite is great for everyday wear however, as with all jewellery, caution must be taken to protect it from harsh chemicals, extreme temperatures and scratches. The best way to clean the stone is with mild dish soap and warm water, using a soft toothbrush.