Birthstone Guide: Alexandrite for Those Born in June

Julia Griffith FGA DGA EG  describes the phenomenal appearances of Alexandrite, the June birthstone - 'Emerald by day, ruby by night'.

This extraordinary gemstone appears green or red dependent on the light that it is observed under – a colour change effect also known as the ‘alexandrite effect’.  The rarity of this material and its chameleon-like qualities makes alexandrite one of the world’s most desirable gemstones.

Chrysoberyl Alexandrite demonstrating colour change. Image from Gem-A archive.
Chrysoberyl Alexandrite demonstrating colour change. Image from Gem-A archive.

In 1834, alexandrite was first discovered alongside beryls within the prestigious emerald mines in the Russian Ural Mountains. It is part of the chrysoberyl family, which is separate to the beryls, being a beryllium aluminium oxide as opposed to a silicate. Chrysoberyls have good durability and a hardness of 8.5 making them perfect for use in jewellery… that is, if you can find one.

Alexandrite is so rare that it has never truly been the main aim of commercial mining but instead a ‘by product’ as the likelihood of uncovering one is very slim. In Russia, just one crystal of alexandrite was found for every hundred-or-so emeralds.

Read more: Emeralds for Those Born in May

In the majority of alexandrites the clarity is poor – they are commonly riddled with fractures and appear translucent to opaque. Such specimens have little value and are often unusable as gems.

Rough specimens over 5 ct in weight are also a scarcity and most alexandrites found on the market are under 1 ct. Prices for fine specimens above 1 ct will rival or surpass fine quality rubies, emeralds and diamonds making them the one of the most expensive and rare gemstones in the world. 

The most important factor for alexandrite is the quality of its colour change. The most prized colour change is a strong raspberry red in incandescent light and a bright green in daylight - however such a perfect specimen is not known to exist.  

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

Alexandrite in tungsten alpha ray. Image from Gem-A archive.
Alexandrite in tungsten, alpha ray. Image from Gem-A archive.
Alexandrite in daylight, gamma ray. Image from Gem-A archive.
Alexandrite in daylight, gamma ray. Image from Gem-A archive.

The hues seen can also vary - if they stray too far from the expected colours of alexandrite or if the amount of colour change seen is minor, the value will be significantly affected and it is debatable to whether it can be classified as an alexandrite at all. 

Read more: The Myths, Legends and Controversy Behind Ancient Preseli Bluestone

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/green respectively) and this has a direct effect on what colour the gemstone appears to the human eye. 

Alexandrites are also noted for their strong pleochroism. This is an independent optical effect from colour change, in which the gem will appear different colours from different directions. In alexandrite the pleochroic colours are green, orange and purple-red.

The finest quality alexandrites are said to be from the original deposits in Russia, which were mined out in the nineteenth century. ‘Alexandrite’ was named for the Russian Tsar, Alexander II. Legend states that this rare and beautiful stone was found on the day the heir became of age on his sixteenth birthday. 

The vibrant red and green colours observed also mirror the colours of the national military of Imperial Russia and alexandrite became the official stone of the Tsardom of Russia. 

Read more: Aquamarine for Those Born in March

According to Russian legend, wearers of alexandrite reap many benefits including good luck, fortune and love. A popular belief is that alexandrite helps the wearer strive to excellence bringing concentration, discipline and self-control.

Nowadays alexandrites are mined from Brazil, Myanmar, Tanzania, India and Madagascar. Sri Lanka has also produced some fine specimens - the world’s largest faceted alexandrite hailed from this locality and is a whopping 65.7 ct! A further rarity is chatoyant or ‘cats-eye’ alexandrites, which are cut in cabochon to reveal this optical effect.

Chrysoberyl alexandrite crystal, cyclic twinning. Image from Gem-A archive.
Chrysoberyl alexandrite crystal, cyclic twinning. Image from Gem-A archive.

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 1960’s and these synthetics have the same chemical, physical and optical properties of natural alexandrite and show a strong colour change - but lack rarity. 

The most common simulant is synthetic colour change sapphire, which shows a greyish blue to pink colour change. At just a dollar or two per carat - it is extremely common on the market. This material has been made since 1909 so is often found in antique pieces of jewellery.

Alexandrite synthetic flux. Image from Gem-A archive.
Alexandrite synthetic flux. Image from Gem-A archive.

A good colour change, good quality, transparent natural alexandrite could easily cost the consumer a five figure sum per carat and beyond in regards to price. A fine price to pay for such a spectacular and exceptional gem. ■

This article was written by Gem-A for the May/June 2017 issue of The Jeweller - The magazine of the National Association of Jewellers

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image red square Moscow, Russia. 


Understanding Selenite

Understanding Selenite

The Gem-A Gemstone & Mineral Collection contains this fantastic selenite specimen with grass-like green blades that shoot-out from the host rock. Assistant gemmology tutor, Dr Juliette Hibou FGA, explains more about the origins and properties of this striking gem material. 

Read more


What Makes A Gemstone Rare?

What Makes A Gemstone Rare?

The term 'rare' is thrown around alot online, but what gemstones actually deserve the term and do diamonds fall into this category at all? Gem-A tutor manager, Rona Bierrum FGA DGA, explores some of the rarest gemstones known to man and considers how rarity is measured in the gem and jewellery trade. 

Read more


What is the Link Between an Emerald and the Emerald-Cut?

What is the Link Between an Emerald and the Emerald-Cut?

Sometimes, we come across terms in gemmology that cause confusion. We all recognise the beautiful green colour of an emerald, but there is also an emerald-cut that has nothing to do with the green gem itself… or does it? Here, we explain the story behind the twisted terminology.

Read more


The Most Underappreciated Gemstone? Why We Love Rock Crystal

The Most Underappreciated Gemstone? Why We Love Rock Crystal

Everyone knows that lucky April-born souls have been blessed with one of the most prestigious birthstones: diamond. However, there is an alternative birthstone for the month and it's a 'hidden gem'... so to speak! Gem-A Member, Julia Griffith FGA DGA EG explains why rock crystal is worth your time and attention. 

Read more


Birthstones Guide: Diamond for Those Born in April

Birthstones Guide: Diamond for Those Born in April

Those born in the month of April can count the illustrious and historically significant diamond as their birthstone. Here, Gem-A tutor Lily Faber FGA DGA EG delves into the past to uncover why diamonds are so valued... and so valuable. 

Read more


Understanding Fossils as Decorative Materials

Understanding Fossils as Decorative Materials

Inspired by a fantastic specimen in the Gem-A Gemstone & Mineral Collection, tutor Pat Daly FGA DGA explores the use of fossils as decorative objects and describes some collectible specimens, like ammonites, trilobites and peanut wood.

Read more


Gem-A Offers Scholarships to Trio of GCDC Award Winners

Gem-A Offers Scholarships to Trio of GCDC Award Winners

Inspired by the level of jewellery design talent on display at the recent Goldsmiths’ Craft & Design Council Awards, Gem-A opted to present not one, but three scholarships to worthy entrants. Discover the designers who have been offered a place on the Gem-A Diamond Grading and Identification course here... 

Read more


Beginner's Guide: What Are the Different Types of Opal?

Beginner's Guide: What Are the Different Types of Opal?

Are you fascinated by the beautiful colours of opal? Do you wish you knew more? Gem-A assistant gemmology tutor, Charlie Bexfield FGA EG presents his beginner's guide to opal types, including common and precious varieties. 

Read more


Top 10 Luxury Brands: The Jewellery Connoisseur's Wish List

Top 10 Luxury Brands: The Jewellery Connoisseur's Wish List

Do you dream about a sparkling high jewellery collection from world-leading brands? Christa Van Eerde MA MLitt FGA DGA discovers the quintessential pieces from the top 10 houses leading the luxury jewellery sector.

Read more


Read the Spring 2019 Issue of Gems&Jewellery

Read the Spring 2019 Issue of Gems&Jewellery

We are pleased to introduce the Spring 2019 edition of Gems&Jewellery magazine, packed full of interesting and informative features for Gem-A Members and current students. Find out how to read the issue online here... 

Read more


Bloodstone: The Alternative March Birthstone

Bloodstone: The Alternative March Birthstone

Perhaps because of its gothic colour palette and unusual history, bloodstone has long been considered the more 'traditional' choice for the month of March. Here, Gem-A gemmology tutor Lily Faber FGA EG delves into the properties of bloodstone, which is sometimes known as heliotrope or 'blood jasper'. 

Read more


Birthstone Guide: Aquamarine for Those Born in March

Birthstone Guide: Aquamarine for Those Born in March

Those born in March are lucky enough to have two birthstones: the beautiful blue of aquamarine and the mysterious red-spotted bloodstone. Here, we delve into the gemmological and mystical properties of aquamarine and why this sky blue gem is said to be a talisman of good luck, fearlessness and protection. 

Read more


Questions To Ask When Buying A Piece Of Gemstone Jewellery

Questions To Ask When Buying A Piece Of Gemstone Jewellery

What are the essential questions to ask a high street store or designer brand when buying a piece of gemstone jewellery? How can you be sure you'll get what you really want? Continue reading to see our checklist of essential conversation starters. 

Read more


Understanding Dioptase

Understanding Dioptase

Did you think this might be emerald? You certainly wouldn't be the first to confuse the vibrant green of dioptase with the more recognisable, jewellery-lover's gemstone. Here, Gem-A assistant gemmology tutor, Dr Juliette Hibou FGA, explains more about the history, properties and origins of dioptase, an unusual collector's gem. 

Read more