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Alexandrite Mines | What It's Like To Be In One

As you admire your favorite piece of jewelry, has the question ever struck you: where did this come from? Sometimes it can be easy to look past the origins of a ring or necklace and even forget that the gem held within once belonged to the Earth. 

By deconstructing the sources of gems, you will create a greater understanding of and appreciation for the hard work that goes into their excavation. At Mark Henry Jewelry, we focus on bringing fine and exotic gems to the masses in accessible, luxurious, and ethical ways.

One of which is our pride, the alexandrite gem. The June birthstone is cuts above the rest and is well known for its color-changing properties - green under daylight and a dazzling red hue once the sun goes down. 

Through our extensive research and close ties to family-run mines that have lasted decades, we have garnered a knowledge of alexandrite mining with unparalleled access to the process itself. 

We hope to share our findings with you and introduce our customers to the incredible work being done that makes their jewelry sparkle so brilliantly. 

What Are We Working With?

Before we jump into any explanation regarding the methods of mining alexandrite specifically, it is best if we begin by presenting the basics of the gem. Alexandrite hails from the Ural Mountains of Russia.

It was discovered in 1834 when mineralogist Nils Gustaf Nordenskiöld led a team of researchers to the location and came up with what at first appeared to be an emerald - upon further inspection, and as the daylight faded, it became clear that he had landed on magic. 

Since alexandrite was discovered in Imperial Russia and happened to bear the same colors as the rulers’ flag, it was named for Alexander II, who was set to become the Czar. Ultimately, he was assassinated not long after, but his legacy remains in the form of this gem.

At the time, Czars were likened to the celebrity status of the British Royal Family today. One can imagine how this catapulted alexandrite to fame within the surrounding communities

Properties of Poise

To further grasp the general idea of this gem, its properties must be noted. Apart from its color-changing phenomena, it is also known for having instances of chatoyancy, a rare cat-eye effect that is incredibly valuable. 

Alexandrite is formed through a combination of beryllium and chromium. Its rarity is pronounced when you consider that beryllium is one of the most scarce elements on this planet, and the mix of the two is unlikely in the same rock. This gem is shrouded in mysticism and chance. 

Here are a few other properties of alexandrite: 

  • Luster: Vitreous. 
  • Hardness: 8.5 on the Mohs Scale (incredibly wearable and versatile in placement). 
  • Birefringence: 0.009-0.010.
  • Heat Sensitivity: Exists. 
  • Luminescence: Weak in red Short Waves and Long Waves, but present. 
  • Transparency: Ranges from opaque to transparent. 
  • Pleochroism: Varies from red/orange to yellow/green. 

When ranking a piece of alexandrite in value or quality, the most important factor is how deep and saturated the color change is. Percentages of changes can range dramatically. Although a clean gem is favored, this property is secondary to the color change. An opaque piece of alexandrite with 90% color change is still highly valuable.

Where Are We Working?

Alexandrite’s color, and makeup, vary depending on where it occurs in the world. After the boom of Russian mining, the supply was quickly depleted by the 1980s, and producers were being forced to look outward.

Thankfully, in the same decade, other supplies were recovered, and the process began all over again. The most notable sources for modern-day alexandrite mining are Brazil, India, and Sri Lanka, among many others. 

Below is an image at the mining facility we work closely with in South East Brazil.

The Mining Process: A Case Study

While no two locations mine for alexandrite in the exact same way, as it is not formed in the Earth the same way, it can be helpful to consider one specific process at a time. Mark Henry Jewelry receives our alexandrite from a family-owned Brazilian mine since our opening in 2004 for alexandrite supplies. Through this intimate relationship, we were able to have full access to the mining process and the ethical upkeep throughout.

Brazilian alexandrite was first obtained in the 1980s. The pegmatite district in Minas Gerais, Brazil, opened its doors to mining the precious gem in response. Over 95% of the region’s cat-eye chrysoberyl (the family that alexandrite falls into) supply was located here from the mid-1800s until the discovery of local alexandrite. This is why the finding may not have come as a surprise since the land was clearly formulated to create such a gem. 

The Americana, Santana, Gil, and Barro Preto Valleys produce some of the rarest, clearest, cleanest, and best color changes in all of the gems’ mines. In 1987, the Lavra de Hematita alexandrite was found, and this supply has provided tens of kilos of the gem that are of the finest quality imaginable with enormous carat size (alexandrite is known for being quite small. Just one carat can go for $30,000). 

Barro Preto and Gil Mines

The claims of Barro Preto and Gil are two of the most prominent spaces for Alexandrite mining in this Brazilian area. They rest at a 750-meter elevation and are regarded as the highlands. They are composed of granite and granitic gneiss, alongside much-scattered pegmatite, which accounts for secondary deposits that boast gem minerals. 

The Barro Preto and Gil valleys are consistent with chrysoberyl-presenting land since they have the same specific gem gravels (called cascalhos) that are needed for production. Cascalhos are underneath layered red soil or black clay and sand.

Gil’s valley specifically produces small and round gem components, compared to the Barro Preto valley, which contains rough and jagged pieces of gem material. It can be concluded that the mother rock for these gem pieces is farther from Gli but closer to Barro Preto. 

The layers of land in these two areas occur as follow: 

  • Red soil that covers the expanse and is lateritic. 
  • A 1.25 meter-layer of black clay combined with sand, conducive to the Barro Preto claims but less common in Gil. 
  • The topmost layer of the cascalho that falls right at the river’s level, which contains gem pebbles and sand. Rounded rocks occur here. The gravel here gets its red tint from iron-oxide that is present. While it can be anywhere between one and five meters thick, the larger it is, the more likely substantial gem material will be found. 15-20 percent of the chrysoberyls that occur in Barro Preto are mined from here. 
  • An organic-matter layer of black clay that occurs after rain forest depletion.
  • A ten to 20-centimeter clay layer that occurs after ancient water source sedimentation (lakes, streams, creeks, etc.). It can be difficult to work with due to its hardness.
  • A layer of fine sand, which can be a varying shade of red, yellow, or white depending on iron oxide content. 
  • The lowest layer is a cascalho, and where additional gems can be found. Here, the gems are combined with granite rocks from the local water source (in this case, a river), quartz gravel, and sand. 

Safeguarding People and the Environment

The process for mining through these layers can be complicated depending on environmental conditions like extreme rains. Hundreds of holes are created by the working miners throughout the valleys in search of gems or gem materials. Pumps are utilized to irrigate the areas as they dig, but temporary breaks are necessary for water not to build up high enough for unworkable conditions.

The cascalho layer is broken through by digging to the floor of the valley. Once the workers have reached this point, they put up wooden beams to support the other layers so they won’t crash down on them while they mine. 

Occasionally, the local water source (river, creek, etc.) has to be rerouted for these jobs to occur. You can’t have a flood bearing down into a small pit that you’ve dug, especially when the land can be quite soft. It can be easier to mine through only the upper layers, specifically the topmost cascalho layer, since gem material does occur here. 

Other concerns for safety arise when granite boulders are present. They can be incredibly heavy and pose a threat if they are unable to be moved and block gem gravel. Hundreds of boulders can be moved during only six weeks of production.

Since the holes the miners work in can be as small as two feet deep, it is essential that any danger be removed immediately for them not to get stuck. 

A Brilliant Experience 

Once alexandrite has been successfully mined, it is placed in a four-screen stack and gently washed with water for the gravel to be cleaned and residue to be discarded.

The tedious work of mining for these gems is not lost on our community of jewelry lovers, and we encourage you to remember their hard work when you’re admiring your latest piece of Mark Henry alexandrite

 

Sources: 

Alexandrite Value, Price, and Jewelry Information | Gem Society

Chrysoberyl and Alexandrite from the Pegmatite Districts of Minas Gerais, Brazil | GIA

GEOGRAPHIC ORIGIN DETERMINATION OF ALEXANDRITE | GIA

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