CHRYSOBERYL 

What Is Chrysoberyl?

By Charlie Foreverdark

Chrysoberyl: The Golden Green Gemstone of Legends

Chrysoberyl is one of nature’s most fascinating gemstones. Despite its name, it does not belong to the beryl family, which includes emerald and aquamarine. Instead, chrysoberyl is a beryllium aluminium oxide with the chemical formula BeAl₂O₄, while beryls are aluminium beryllium silicates.

The name Chrysoberyl comes from the Greek words chrysos, meaning “gold,” and beryllos, referring to the blue green colour of seawater. Together, the name translates to “golden green.”

Physical Properties

Chrysoberyl ranks as the third hardest commonly encountered natural gemstone, measuring 8.5 on the Mohs Hardness Scale. It is harder than topaz and only slightly softer than corundum, the mineral species that includes ruby and sapphire.

Because of its exceptional hardness, chrysoberyl resists weathering and erosion remarkably well. As a result, prospectors often recover it from stream gravels and alluvial deposits long after the surrounding rocks have broken down.

However, despite its hardness, chrysoberyl remains a brittle mineral. It has one direction of distinct cleavage and two less obvious cleavage directions.

Chrysoberyl commonly forms:

• Tabular crystals
• Prismatic crystals
• Striated crystals
• Twinned crystals

Occasionally, nature produces spectacular crystal forms, including:

• Stellate (star shaped) crystals
• Hexagonal twins
• Rosette formations

Furthermore, chrysoberyl belongs to the orthorhombic crystal system, meaning its crystals develop along three unequal axes that meet at right angles. It also has a vitreous lustre and displays double refraction, where light splits into two rays as it passes through the crystal.

Iron impurities create most yellow and green chrysoberyls. However, rare mint green specimens from Tanzania owe their colour to traces of vanadium.

How and Where Does Chrysoberyl Form?

German geologist Abraham Gottlob Werner officially named the chrysoberyl mineral group in 1790.

Because chrysoberyl requires unusually high concentrations of beryllium, it forms in relatively few geological environments. Most commonly, it develops during the final stages of magma crystallisation inside pegmatites, coarse grained igneous rocks that cool slowly beneath the Earth’s surface. This slow cooling allows exceptionally large crystals to grow.

The word pegmatite comes from the Greek pegnymi, meaning “to bind together,” a reference to the large interlocking crystals found within these rocks.

Where pegmatitic fluids contain abundant beryllium, both beryl and chrysoberyl may crystallise. Beryl forms when beryllium dominates, whereas chrysoberyl develops where aluminium becomes more abundant.

In addition, chrysoberyl also occurs in metamorphic rocks associated with pegmatites, including dolomitic marble and mica schist.

Occasionally, chromium joins the mix alongside beryllium and aluminium. When this happens, particularly in Russia’s Ural Mountains, the spectacular colour changing variety known as Alexandrite forms.

Today, miners recover chrysoberyl primarily from:

• Sri Lanka
• Myanmar (Burma)
• India
• Madagascar
• Tanzania
• Pakistan
• Brazil
• The United States

Types of Chrysoberyl

Ordinary Chrysoberyl

Ordinary chrysoberyl ranges from almost colourless to vivid yellow green and rich honey gold.

Collectors highly prize transparent stones with strong colour because skilled gem cutters can transform them into exceptional jewellery. Generally, the most desirable colours include:

• Bright yellow
• Golden green
• Apple green
• Rich honey brown

Historically, gemmologists referred to ordinary chrysoberyl as Chrysolite. However, they also used the same name for the unrelated mineral Peridot, creating considerable confusion. Consequently, modern gemmology abandoned the term.

Cymophane: The Cat’s Eye Chrysoberyl

Perhaps the best known variety is Cymophane, more commonly called Cat’s Eye Chrysoberyl.

Its name comes from a Greek word meaning “appearing like a wave,” which describes its silky appearance.

Most importantly, cymophane displays chatoyancy, a striking optical effect where a bright silver white band of light glides across the stone as it moves. Thousands of microscopic parallel needle like inclusions create this remarkable phenomenon.

When lapidaries cut the gemstone into a cabochon, the reflected band resembles the narrow pupil of a cat’s eye.

In addition, many fine specimens display the famous Milk and Honey Effect, where one side of the stone appears lighter than the other depending on the angle of the light.

Although several gemstones exhibit chatoyancy, jewellers usually mean Cymophane Chrysoberyl whenever they simply refer to a Cat’s Eye gemstone.

Consequently, expert cutting becomes extremely important. A stone cut too shallow develops a broad, indistinct eye, while a stone cut too high often produces an off centre eye. Perfect examples command exceptionally high prices.

Alexandrite

Alexandrite represents the rarest member of the chrysoberyl family.

Unlike ordinary chrysoberyl, Alexandrite changes colour dramatically. It appears green in daylight before shifting to red under incandescent light. Chromium within the crystal structure creates this extraordinary optical effect.

Consequently, Alexandrite remains one of the world’s most valuable coloured gemstones.

A History of Chrysoberyl

For thousands of years, people have surrounded chrysoberyl with myths and legends.

Throughout Asia, many believed the gemstone protected its owner from the Evil Eye. Likewise, people in ancient Sri Lanka wore chrysoberyl as protection against evil spirits.

However, local folklore also warned that dreaming about a Cat’s Eye gemstone suggested deceitful or treacherous behaviour.

By the end of the first century AD, Cat’s Eye Chrysoberyl had become well known throughout the Roman Empire.

In Hindu tradition, a green Cat’s Eye Chrysoberyl decorated the symbolic necklace of Lord Vishnu, where it represented the magnetic centre of human passion.

Centuries later, Spanish and Portuguese jewellers embraced Cat’s Eye Chrysoberyl during the eighteenth and nineteenth centuries. Its popularity increased dramatically after the Duke of Connaught presented his fiancée with a Cat’s Eye Chrysoberyl engagement ring. As a result, demand for fine Sri Lankan stones soared.

Famous Chrysoberyls

The Eye of the Lion

The world’s largest known cut Cymophane Chrysoberyl weighs an astonishing 465 carats.

Miners discovered the original crystal, which weighed more than 700 carats, in the gem rich gravels of Pelmadulla, Sri Lanka, during the late nineteenth century. The owning family preserved the rough crystal for decades before commissioning a master gem cutter in 1930.

Today, the Smithsonian Institution recognises The Eye of the Lion as the largest cut chrysoberyl in the world.

The Hope Chrysoberyl

The Hope Chrysoberyl, now displayed in London’s Natural History Museum, weighs 45 carats.

After its discovery in Brazil around 1821, renowned collector Henry Philip Hope purchased the rough crystal for just £250. Gemmologist Herbert Smith later described the finished gemstone as “absolutely flawless.”

Today, experts value the gemstone at well over £100,000.

The Kandy Cat’s Eye

The magnificent 313.5 carat Kandy Cat’s Eye once formed part of the Crown Jewels of the Kingdom of Kandy in Sri Lanka.

In 1886, officials presented the gemstone to Queen Victoria, who already admired chrysoberyl jewellery and owned several pieces gifted by Prince Albert.

The Maharani

The Maharani Cat’s Eye, now part of the Smithsonian collection, ranks among the finest Cymophane Chrysoberyls ever discovered.

Originally mined in Sri Lanka, the gemstone weighs 58.19 carats. Its delicate honey colour, razor sharp eye and incredibly fine silk inclusions place it among the world’s finest examples.

Watch Out for Fakes

Unfortunately, manufacturers have produced synthetic Cat’s Eye gemstones since the 1970s, and they have sold them commercially since the 1980s.

Fortunately, natural and synthetic stones usually display obvious differences.

Natural chrysoberyl typically shows:

• Straight, parallel needle like inclusions
• Natural internal imperfections
• No gas bubbles

By comparison, synthetic stones often contain:

• Curved or undulating fibres
• Exceptional clarity
• Gas bubbles
• Yellow fluorescence under ultraviolet light

Therefore, experienced gemmologists can usually distinguish natural chrysoberyl from laboratory grown imitations with relative ease.

Final Thoughts

From the mesmerising moving eye of Cymophane to the dramatic colour change of Alexandrite, chrysoberyl remains one of the world’s most remarkable gemstone families.

Not only does it possess exceptional hardness and rarity, but it also boasts fascinating optical effects and an extraordinary history. Whether displayed in museum collections, treasured by collectors or worn as fine jewellery, chrysoberyl continues to earn its place among the world’s most captivating gemstones.