The Mining of Alexandrite Gems

Alexandrites are among the rarest gemstones in the world. The difficulty of sourcing them, in addition to their trademark colour changing character has made them a valuable possession for gem enthusiasts, fine jewellery companies, and those who simply wish to own top quality colour change gemstone as a part of gemstone or jewellery collection. The appeal of alexandrite gems is their extreme rarity in nature, which means that geologists and gem miners are required to exert a great of effort in sourcing them and then brining them to the market. If you are curious to know why this is so, and what factors alexandrite gemstone miners, and other stakeholders involved in this process look for in sourcing these color change gems, then this education page is for you.

The Mineral Character of Earth and Rarity of Certain Minerals

When it comes to gemstones and their rarity in relation to other, more commonly found minerals and crystals which are more abundant but, one needs to look at the mineral character of Earth. Our planet features an array of minerals and mineral combination at varying levels of concentration and abundance, differing between lighter and heavier elements. At the crust of our planet, which is a the region where many of the precious gems develop over the course of millions of years, a handful of minerals dominate: Oxygen, silicon, and aluminium. Followed by lowers levels magnesium, calcium, and potassium. When it comes to precious gemstones like alexandrites, along with other top gemstones like emeralds, these fall into less than one percentage of other rare minerals, such as beryllium. So the challenge when it comes to sourcing not such alexandrites, but relatively more abundant gems like emeralds becomes a challenge owing to the mineral makeup of Earth.

Factors that contribute to Alexandrite development

When it comes to the development of alexandrite gems two main conditions need to be in place for these gems to develop: the chemical condition and physical conditions or external conditions. For the formation of alexandrite gems, and this is true for other gemstones as well, the right chemical factors need to be in place. These include the presence of oxygen (fugacity); the Ph level (acidity); and critically the mineral character of the environment. In the case of alexandrite gems, the presence of beryllium, aluminium, oxygen, along with key with trace minerals like chromium and vanadium being necessary for their formation. Then there are physical conditions, which provide the external pressure and input that push these chemical conditions to give rise to alexandrite gems. These include environmental pressure, the optimal, temperature and importantly time.

When it comes to the mineral character of the minable environment, the concentration pegmatite: which is a crystalline rock that forms during the hardening of magma is key. As in pegmatite sources, the rarer elements that produce gemstones like alexandrite tend to concentrate. Thus finding these pegmatite rock formations are the place to look when it comes to identifying a common first marker for alexandrite stones, and they are the beryllium deposits: which is the main source for emeralds.

However things get interesting with respect to alexandrite stones, which needs the presence of chromium. Which is extremely rare in beryllium deposits. Going further, what makes alexandrite even more rarer, much rarer than emeralds is the that it entails the absence of silica. Which is an extremely abundant mineral in the natural world.

Essentially an emerald forming environ, but minus the silicate. In countries like Russia and Tanzania alexandrite and emeralds are found together. Temperature is also a key factor, where higher temperatures tend to correspond to higher chrysoberyl formation, which is the first step in denitrifying alexandrite sources. Where higher levels of aluminium with lower silicate presence are key factors.

Alexandrite Mining Sources

Alexandrite stones are mined from two different sources: from regions where the gemstones are found in the place of their formation, the primary source. Or in regions where the gems have moved from their original place to a different location. Primary sources refers to gems which are mined directly from the rocks in which they for. These tend to be found in lower concentrations, and in various mineral qualities. Mining from primary sources is a more complex process, and requires greater expertise of the mining process.

Secondary alexandrite sources could be gems found in weathered rocks, or in other natural sources like river beds, and sea bed, and near desserts sands. Such gemstones are understood to be transported by forces like gravity, tidal action, natural factors environmental, breaking down, The stones that survive the process are often of a higher quality and tend to be larger. Alexandrite from secondary sources are easier to mine, as they are separated from host rocks, and also tend to be found in higher concentration. The geology surrounding secondary alexandrite sources is still an evolving process.

The Mining of Alexandrite Stones

Given the rarity of alexandrite in the natural world, the sourcing of these gemstones often emerge as a secondary or tertiary mining process. Often miners and geologists seek out beryllium sources, which are relatively rare. Of which emeralds follow as secondary source, being the rarer mineral. Following the mining of emeralds, alexandrite may emerge as a third factor. Which in such unfed sources, will entail the manual separation of the particular gemstone. This is a predominant feature in countries like Russia. However the presence of emerald as an indicator for the presence of alexandrite is not a given, with countries like Colombia despite being strong producers of emeralds produce virtually no alexandrite gems. This is due to the high concentration of beryllium being complimented with very high levels of silcate, which works against the chemistry of alexandrite gems.

The Popularity of Secondary Alexandrite Sources

In countries like Ceylon, Tanzania, alexandrite are mined primarily from secondary sources. The actual origins of these gemstones in such secondary sources is still being a subject of study, as geologists are reasearching ways of finding the link between the primary source in which the alexandrite gems formed and where they ended up in river beds, along with other gemstones like sapphires in countries like Ceylon. One explanation is that alexandrite have higher specific gravity: which helps the gemstone remain fixed in a certain secondary deposit, like gravel or

The mining for alexandrite in countries like Sri Lanka is often a secondary by-product of sapphire mining. With gemstones that are not sapphires being subjected to further analysis, producing other gems. In countries like Madagascar, where the mining of these stones takes place in more arid conditions, where there is an dearth of water. Which present different logistical challenges, as the character of the secondary source is a different one.