Chrysoberyl and Alexandrite: What Are They, And What's The Difference?

In this article, you’ll learn about Chrysoberyl and Alexandrite, and by the end, hopefully you’ll be able to explain the difference between them.

Chrysoberyl and Alexandrite (EXPLAINED)

Introduction

Are alexandrite and chrysoberyl really different stones?

The answer is yes, but not much different.

Both have the same chemical composition: BeAl2O4.

The difference is in their color-changing properties.

Alexandrite changes from green to red in incandescent light, while chrysoberyl changes from a golden yellow to an olive green color.

This change is caused by the phenomenon called pleochroism, which occurs when white light enters a stone and splits into two rays as it passes through the crystal structure of that stone (like passing through a prism).

One ray remains as white light (although actually containing all colors), and the other ray changes.

Pleochroism is what causes alexandrite and chrysoberyl to change color.

Alexandrite

The true red-green variety of chrysoberyl (alexandrite) that exhibits this color-change phenomenon is extremely rare and valuable, especially in larger sizes.

As such, it tends to be more expensive than the golden yellow type of chrysoberyl found in your local jeweler’s case.

Alexandrite has been called “the most beautiful stone in the world” due to its incredible green-red color change.

Unscrupulous jewelers have tried to pass off green alexandrites as real alexandrites, but if you know what pleochroism is and look at the stone carefully, you can usually spot a fake alexandrite.

Alexandrites and other true alexandrites can usually be distinguished from green chrysoberyls because green chrysoberyls are generally more transparent, whereas alexandrites are typically translucent.

Chrysoberyl

Chrysoberyl is the second-hardest gemstone known after diamond, making it very durable for everyday wear, which is why it’s often found in high-quality jewelry.

It has an attractive vitreous luster (glassy brilliance), which contrasts nicely with its vivid color change.

Chrysoberyl is mined throughout the world, with the most notable deposits being found in Sri Lanka.

Chrysoberyl’s color-change properties have been known since ancient times, but Alexandrite wasn’t discovered until 1831 in Russia by amateur mineralogists Prokofieff and Snegirev as they were collecting samples from some newly exposed rock outcrops on one of their expeditions into Siberia.

They named it after Tsar Alexander II of Russia.

The original location where those first chrysoberyls were found is still being produced today. In gemology textbooks, this type of chrysoberyl is called chrysoberyl cat’s eye due to its property of being able to split light along its length and sparkle like a cat’s eye.

Chrysoberyl was first found in Minas Gerais, Brazil, back in 1812.

However, it wasn’t determined as a separate mineral from beryl until 1847.

In the 1800s, chrysoberyl was mined almost exclusively for its industrial use as a refractory material used to make crucibles that would withstand very high temperatures (upwards of 2200°F or 1200°C).

These crucibles were then used by jewelers and watchmakers as well, but it wasn’t until after World War II that chrysoberyl started gaining popularity as a gemstone.

Types of Chrysoberyl

There are different types of chrysoberyl (variations in the chemical and mineralogical formula) and they all have different properties:

Brazilian type: Found at many locations around the globe, including Minas Gerais, Brazil, Maine, Sri Lanka, Tanzania, Kenya, Nigeria, Pakistan. Nuclear glassy material with high birefringence (double refraction) as well as pleochroism. Cat’s eye effect is possible.

Zimbabwean or African type: Similar color to Brazilian but with less dispersion. Found only in Zimbabwe, Africa.

Afghanistan or Transparent type: Also similar to the Brazilian variety both in appearance and dispersion, found only in Afghanistan.

Sri Lankan, Ceylon, or Tapoloka type: Has an orange-yellow to a greenish-yellow color similar to peridot. Found only at one location in Ratnapura, Sri Lanka.

Alexandrite type: Similar appearance as the Brazilians, with red or green color change instead of just green or red like the regular chrysoberyls. Only found around the Ural Mountains in Russia and some other nearby locales.

Chinese or Imperial type: With very little dispersion, they’re commonly used for classic diamond engagement rings since they’re fairly inexpensive compared to other gemstones and diamonds alike.

The largest known chrysoberyl was found in the United States in 2003 and weighed in at a whopping 1,905 carats.

It shattered all previous scale records for weight and size since it was so massive.

However, its weight was slightly deceiving because around 10% of the material couldn’t be cut due to fractures throughout the stone.

Keep that in mind when buying one of these.

Alexandrite seems to be more popular than regular chrysoberyl not just for a color change, but also because they’re often much less expensive.

The color-changing effect isn’t as dramatic as in regular chrysoberyls, since only two faces are green instead of three.

Also, note that even though it may be called alexandrite because of its color change effect, it doesn’t necessarily mean that it’s from Russia.

Most alexandrite types are currently mined in Brazil and Sri Lanka.

Identification

Most alexandrite gems will have a secondary color which you can see by viewing them at an angle or with oblique lighting.

This secondary color is usually yellowish-green or brownish red depending on the transition temperature range between red to green light.

In most cases, this type of coloring shows up as a gray or purplish tone, since there’s less absorption of the green wavelengths than the red ones.

However, if you notice that your stone has very little color zoning or banding, then this secondary color may appear more vividly as a yellow or orange hue due to greater wavelength absorption from those colors.

In the case of larger alexandrite gemstones, the gray or purplish tone may dominate and turn the stone dark, lifeless, and non-preferable as a jewel item unless it’s extremely large and therefore costly enough to be considered more of a collector’s item than anything else.

As with other chrysoberyls, this type is normally cut en cabochon, since its high birefringence makes even the best step cuts sparkle less than their more expensive counterparts, such as diamond or sapphire.

If you’re considering buying an alexandrite, take a look at either Ceylon (Sri Lankan) or Transparent material, also known as Tapoloka or Zimbabwean.

Buying

Regardless of origin, most stones will come with very noticeable color zoning (banding) which is normal for this material.

Both types of chrysoberyl are usually heat-treated to improve their clarity, but it’s not always the case that some deposits may be naturally occurring in an almost completely clear variety.

Also note that, like other chrysoberyls, these stones are meant to be viewed in oblique lighting where you’re sitting under a bright light source at eye level while holding the gemstone up and looking across its surface at about a 45° angle.

If your budget can afford only one stone, it is highly recommended to choose either Brazilian or African gems over Chinese or Russian ones because of their price versus value ratios.

Even though diamonds are well known for their perfect luster, that doesn’t mean anything if it’s hidden underneath too much color.

Nobody ever complained that the Hope Diamond didn’t sparkle like a gaudy circus showpiece, but it’s definitely not one you’d consider to be an attractive option for an engagement ring either, due to its poor color saturation (varying from grayish brown to yellowish-green) and bad clarity.