Alexandrite: The Colour Change Gemstone

_{Alexandrite Crystals on a Green Beryl Rock}

The world of gems is filled with a wide variety of precious stones, with each notable type distinguished by one or more factors; as gemstone merchants, gemologists seek to acquire gems for their uniqueness and rarity, with the hope of bringing to market a valuable gemstone. The gemstone industry is currently dominated by the top four gemstones: diamonds, sapphires, rubies and emeralds. When one speaks of a precious stone, the mind invariably would to one of these gems, with diamond being the most dominant. Indeed given the dominance of the carbon-based gemstone, the other gems in the category have had to distinguish themselves in other ways, with their distinct colours being a notable feature, in addition to other factors with respect to the stone’s character, all of which correspond to the varying degrees of the rarity of the stone. As you may have noticed the key distinguishing feature of any gemstone is its rarity: a rarity in terms of the broader gemstone type, and rarity with respect to specific qualities that a gemstone in a certain group is able to exhibit. As gemstone seekers, gemologists and fine jewellery buyers are united in their wish to be in possession of a stone that is not only rare but distinguishable among its peers. Enter the alexandrite: the colour change gemstone.

What are Alexandrites?

Alexandrites are a variant in the chrysoberyl mineral group: which is a type of beryllium aluminium oxide, meaning it differs from silicate varieties of minerals that are found under the beryl category. This is important since, there is a tendency to view alexandrite stones as a part of the beryl family minerals, which includes the high percentage of beryllium: which is a silver-white metal. The beryllium group of gemstones is better known in the gemstone industry, with the top variants such as emeralds, aquamarines, and to a lesser extent morganite stones leading the way. In this regard, alexandrite, as a variant in the chrysoberyl group of stones are different from beryl stones, in that they contain a greater level of aluminium.

The Origins of alexandrite gems go back to imperial Russia when these stones were first discovered near the Ural mountains, in the 18^th century. It is believed this gem was discovered on the day of Prince Alexander II's birthday, the future Emperor of Russia, and the gem was named after him. At first, confused for emeralds, the gems upon exposure to the light of a fire, the colour seemed to change to red, and so began the journey of the colour change gemstone. Given its rarity and distinction Alexandrites soon become the national stone of Russia. However the supply of these gems soon ran out, until new sources were discovered in Ceylon, with some reports suggesting that these stones were found at the same time as they were in Russia, and later in India, Brazil, followed by some African nations which began to enter the mix, most notably Zimbabwe.

Alexandrite Countries of Origin

Alexandrites stand apart from the crowd in being one of the rarest gemstones in the world. As noted in the table they are rarer than diamonds and even sapphires which are rarer than the popular carbon-based gemstones. Interestingly, alexandrite is rarer than rubies which are the red variant in the corundum family of crystals, which makes these stones extremely rare. With gem-quality stone that can feature in an engagement ring with its key colour-changing feature being a steal. The rarity of alexandrite stones is based on the handful of countries that are able to produce gem-quality stones. As noted, whilst Russia was once the leading source, in the decades past its known sources have been virtually depleted, with new players entering the mix. Notably Brazil. However, the presence of gem-quality stones is still rarer. In recent times certain African countries have entered the mix, however, their capacity provides stones with respectable character, and good colour has been a challenge. Whilst chrysoberyl deposits have been found across the world, the alexandrite variant has been a rarity. The emergence of a number of African nations has brought in much need supply of these rare gemstones, but there are only a handful of such mines in these countries, with even large players like Brazil being able to mine these gemstones from a select number of mines, such as the Itaitinga mine in the state of Minas Gerais, which is known for producing high-quality alexandrite stones leading the way.

Distinguishing Features of Alexandrite Gemstones

What sets alexandrite from other stones in the chrysoberyl family is its colour changing character, which is a function of the presence of chromium, in places where aluminium would be present. For in the case of the chrysoberyl stones in general there is a greater level of iron, thus when it comes to high-quality alexandrite that can produce the colour change feature, it would come down to adequate levels of chromium which can react to the exposure of light. In some extremely rare instances, chrysoberyl stones come with trace amounts of vanadium; a variety of alexandrite that features a cool mint green hue.

As to what sets specific, high-quality alexandrite stones apart from the rest: this comes down to a number of factors: When speaking of cut alexandrite stones, the quality of the cut aside, the clarity of the stone must be accompanied by a solid single colour: which should be either bluish-green or purplish or pinkish-red. As some alexandrite stones tend to feature a brown tone, which gemologists view unfavourably. Which despite their cut, may not produce the contrasting colour change from green to red and vice versa. The colour change feature is the main selling point, which as noted, corresponds to the presence of the trace elements vanadium and chromium. However, their stable colour, and critically the colour change, corresponds to the trace elements' interaction with light. The science of gemstone colour change is best saved for another time, but it is important to note that light and the chemical character of the gemstone working together is what produces these changes. 

Reasons for Owning an Alexandrite Gemstone

The simple reason is the opportunity to stand out. Not many people in the world are aware of these precious gems, and even far fewer numbers are in possession of this gemstone, and an even smaller number are in possession of gem-quality stones that can make it onto an engagement ring. If your aim is to own a ring of great value, and immense rarity then it is tough to get a better option than the alexandrite. Being among the rarest gemstones in the world, and one of the very few stones that can produce a natural colour change effect, alexandrite gems are among the best. So if you are serious about going to a top gemstone, for an engagement ring, then the alexandrite engagement ring is the way to go.