Alexandrite

How alexandrite's colour change works

Alexandrite changes colour because of how it absorbs light, not because of any trick of the cut. The stone carries trace amounts of chromium (and sometimes vanadium), which let it pass green light strongly while transmitting red in a narrow band. Under daylight or fluorescent light, which is rich in blue and green, the stone reads green to bluish-green. Under incandescent light from an old-style bulb, candle, or warm lamp, which is rich in red, the same stone reads red to purplish-red. The GIA records its colour as bluish green in daylight and purplish red under incandescent light.

The strength of that shift is the single biggest thing that decides a stone's quality. A weak change that only hints at a different colour is far less valuable than a clean, obvious flip from green to red. When people search for "alexandrite colour change," that dramatic, complete swap is exactly what they are picturing, and it is genuinely uncommon even among alexandrites. Most modern LED household bulbs sit somewhere between daylight and old incandescent in their colour, so the change can look softer at home than it does under a jeweller's warm lamp. On our Coquitlam bench we always show a colour-change stone under two light sources before anyone commits, because the photo on a phone almost never tells the truth about how it shifts.

Durability: how alexandrite holds up

Alexandrite is a hard, tough stone. At 8.5 on Mohs it sits just below sapphire and ruby (both 9) and well above quartz and most softer coloured stones. More importantly, chrysoberyl has excellent toughness and no cleavage, which is a built-in plane of weakness that makes some gems prone to splitting if knocked. The absence of cleavage means alexandrite resists chipping better than a stone like emerald, which is brittle and famously fragile. That combination makes alexandrite one of the few coloured stones that genuinely earns a spot in an everyday engagement or right-hand ring.

For care, alexandrite is undemanding. Warm soapy water and a soft brush keep it bright, and because it has no cleavage and is rarely fracture-filled, it tolerates ultrasonic cleaning better than many gems. Still, take a ring off before heavy work or the gym. Hardness protects against scratching, but no stone enjoys a direct hit against concrete or a car door. For how 8.5 compares with the rest of the coloured-stone world, see our Gemstone Guide: Durability, Colour & Care, Stone by Stone.

Natural versus lab-grown: where the money goes

This is the part that surprises people most. Natural alexandrite forms only where beryllium and chromium happen to meet in the same rock, two elements that almost never share the same geology, which is why fine material is so scarce. It was first found in Russia's Ural Mountains in the 1830s and named after the young Tsar Alexander II. Fine natural stones over a carat with a strong, clean colour change are genuinely rare, and the American Gem Society notes that high-quality alexandrite can be more expensive than diamond.

Lab-grown alexandrite is the same mineral with the same chemistry, hardness, and colour-change behaviour, grown in a controlled setting instead of in the ground. The International Gem Society explains that lab-created alexandrite is real alexandrite, identical in its physical and optical properties, and the better hydrothermal-grown material can be hard to separate from natural without lab equipment. The practical upshot: a lab-grown stone gives you the green-to-red drama in a clean, sizeable gem for a small fraction of natural prices, while a natural stone is bought as a rare collectable as much as a piece of jewellery.

One labelling note. Under U.S. and Canadian trade rules, man-made stones must be described with a clear qualifier such as "laboratory-grown," "laboratory-created," or "[maker]-created," never sold plainly as alexandrite without it. If a deal looks too good for a "natural" stone, it almost certainly is lab-grown or a simulant, and an independent report should clear it up. The GIA does not assign a quality grade to alexandrite the way it grades diamonds, but it will issue a Colored Stone Identification report stating whether a stone is natural or lab-grown and noting any treatments.

Choosing and wearing alexandrite

If you want the look without the natural-stone price, lab-grown is the sensible call, and it is what most alexandrite jewellery on the market actually uses. If you specifically want a natural stone, insist on an independent identification report stating origin, and judge it first on the quality of the colour change, then on clarity and size. Either way, set it where the colour shift can be seen, alexandrite rewards a design with open sides that let light reach the stone.

Because alexandrite leans toward green and red, it pairs well with both white and yellow gold and works as a striking alternative to the usual blue and red corundum. If you like the idea of a colour-change centre but want to compare options, our guide to Beyond Diamonds: Alternative Stones walks through the trade-offs. You may also want to read up on the harder, more familiar coloured stones: Sapphire, Ruby, and the softer but storied Emerald.

Frequently Asked Questions