Alexandrite

What is alexandrite?

Alexandrite is the color-change variety of chrysoberyl, a beryllium-aluminum oxide with the chemical formula BeAl₂O₄. It shares its mineral species with ordinary chrysoberyl and with cat's-eye chrysoberyl, but alexandrite is set apart by its remarkable optical behavior.

It has a Mohs hardness of 8.5, which places it just below corundum (ruby and sapphire) and makes it highly durable. Its refractive index is about 1.746–1.755.

What gives it its color change?

The color change is caused by trace amounts of chromium in the crystal structure. Chromium changes how the stone absorbs and reflects different wavelengths of light, so the same stone can look visibly different depending on the light source.

In natural daylight, alexandrite typically appears green, teal, or bluish green. Under incandescent light, those tones shift toward raspberry, burgundy, or purplish red. Some stones show a subtle transition, while others shift dramatically. Some also show pleochroism, revealing slightly different hues when viewed from different angles.

Where does alexandrite come from?

Alexandrite was first discovered in the Ural Mountains of Russia in 1830 and named in honor of the future Czar Alexander II. Those early Russian stones remain among the most historically significant alexandrite ever found.

Today the main commercial sources are Brazil, Sri Lanka, and East Africa. Brazilian material often shows a strong green-to-red shift, while different sources produce slightly different color characteristics.

Natural rarity and lab-grown alternatives

Natural alexandrite is extraordinarily rare and expensive, and fine stones with vivid color change are difficult to source in any size. Larger stones are even less common, and value rises sharply with carat weight.

Lab-grown alexandrite is also available. It has the same chemical composition and crystal structure as natural alexandrite and displays a similar color change, typically at a much lower price. The distinction between natural and lab-grown should always be disclosed, and it matters enormously to value.

How to judge alexandrite

Color change is the single most important factor. The most valuable stones show a strong, high-contrast shift between green and red. A smaller stone with a vivid color change is often more desirable than a larger stone with a muted one.

Clarity matters too, because a cleaner stone lets the color change appear sharper and brighter. Cut also affects the effect: a well-proportioned cut maximizes light return. Always view alexandrite under at least two light sources, natural daylight and warm incandescent light, before deciding.

Jewelry and care tips

With a hardness of 8.5 and no cleavage, alexandrite is durable enough for everyday wear and suits rings, pendants, and earrings. Clean with mild soap, warm water, and a soft brush.

Avoid harsh chemicals and extreme heat, especially in pieces that contain other, softer gemstones or delicate settings. Store separately from softer stones to minimize scratching.

Cultural beliefs and symbolism

Alexandrite's visible color change has long connected it with transformation and adaptability, and its "emerald by day, ruby by night" reputation gave it a sense of rarity and prestige from the moment it was discovered.

It is one of the official birthstones for June, alongside pearl and moonstone, and the traditional gemstone for the 55th wedding anniversary.

These are folkloric and cultural traditions.

What affects its value?

Value is driven first by the strength and contrast of the color change, with a clear green-to-red shift commanding the most. Clarity, cut quality, carat weight, and origin follow, and natural stones are worth far more than lab-grown material of the same appearance.