There is a moment at every open house when we pull out the small alexandrite tray and the room goes quiet. Someone holds the stone up to the window, then walks under a lamp, and the color actually moves. Green to red. Teal to purple-gray. The stone is not changing; the light is. That optical trick is the whole story of alexandrite, and it is why the gem has spent two centuries as one of the most coveted colored stones on earth.
The science behind the shift
Alexandrite is a variety of chrysoberyl, colored by trace chromium — the same element that colors emerald and ruby. Unlike those stones, alexandrite absorbs light in a narrow band across the visible spectrum. Daylight, which is rich in blue and green wavelengths, makes the stone read green. Warm incandescent light, which is rich in red, makes the same stone read red. The eye sees a different dominant color depending on which part of the spectrum the light source is pushing.
This effect is called pleochroism of a specific kind, but in practice jewelers just call it color change. The strongest change — a clear green in daylight flipping to a raspberry red under warm light — is the grade that commands collector prices. Stones that shift from muddy teal to brownish purple are real alexandrite, but they are a long way from the famous Russian material.
Where alexandrite comes from
The original deposits were in the Ural Mountains of Russia, first described in the 1830s and named for the future Tsar Alexander II. Those mines are largely depleted. Today's notable sources include Sri Lanka, Madagascar, Tanzania, and Brazil. Sri Lankan material tends to be lighter and less strongly changed; Madagascar and Tanzanian material sometimes approaches the classic Russian shift, usually at smaller sizes.
Fine natural alexandrite above one carat with a strong color change is genuinely rare. Prices per carat for clean, well-cut material can climb into the thousands — and above the famous color-change threshold, into the tens of thousands. At sizes above five carats, you are looking at collector-level pricing and paperwork.
Natural vs. lab-grown alexandrite
Here is the conversation we have more often than any other on this stone: lab-grown alexandrite. Chemical vapor and flux-grown synthetic alexandrite has been on the market for years, and it is physically and optically identical to the natural material. The color change is real. The hardness is real (8.5 on Mohs, just below sapphire). What differs is the price and the story.
We are not snobs about it. A well-grown lab alexandrite in a custom mounting is a beautiful ring that will last a lifetime. We will set it, polish it, and service it the same way we would a natural stone. What we will not do is sell a lab stone as a natural one, and we will always write the origin on the paperwork. If the price on a 3-carat alexandrite looks too low for the color change you are seeing, ask the question directly.
Cutting alexandrite
Because the color depends on which wavelengths reach the eye, the cut matters more for alexandrite than for almost any other colored stone. A cutter who does not understand the pleochroism can face up the weak side of the crystal and end up with a stone that looks brown under every light. We source alexandrite already cut, but we will turn away a stone that face-up looks lifeless in either light source. The bench test is simple: window light, lamp light, and then ask whether the stone looks different — not just slightly different, but recognizably different.
Alexandrite's hardness of 8.5 makes it one of the most durable colored engagement stones available. It takes a prong setting, a bezel, even an everyday band without complaint. It has no dangerous cleavage, no oiling, no special handling. If you can live with the price, it will outlast you.
How to shop for alexandrite honestly
The one question that matters when you are shown an alexandrite is simple: "What does it look like under both daylight and incandescent light?" A reputable dealer will have two lamps on the stone table specifically so you can see the shift. If the stone looks the same color under both lights, the change is weak and the price should reflect that. If the color shifts dramatically, ask for a written origin and treatment disclosure. Fine natural alexandrite should come with paperwork; a stone at a price that looks like glass is usually either lab-grown or heavily included material being sold on the strength of the name.
Care
Warm soapy water and a soft brush are perfectly safe. Ultrasonic cleaning is fine on clean, un-included material; we still prefer steam-off, because some alexandrite contains internal fractures that heat can widen. Treat it like a fine sapphire and you will not go wrong. The only real risk to an alexandrite ring is a hard knock that chips the girdle, which is true of any faceted stone at this size.
For more on how cut and light interact in colored stones, see our piece on facet angles and brilliance, and for other stones that pair an unusual look with everyday durability, our list of underrated colored gems for engagement rings. Alexandrite is not a stone you buy on a budget. It is a stone you buy because you want the one that changes with the room.
The definition of carat weight and how it is measured are set out in the Wikipedia entry on carat weight.
Related reading: Aquamarine Gemstone: Properties, Color, and Value Explained, Colored Gemstone Buying Guide: How to Evaluate Color, Clarity, and Cut, Amethyst Gemstone: Color, Heat Treatment, and Care.
Frequently Asked Questions
How do I verify a factory before placing a bulk order?
Request a production video, business license, export records and a paid sample run. A factory that accepts a 50-piece test order is usually a real manufacturer.
What payment terms do you offer?
30% T/T deposit with the balance against the bill of lading. This protects both sides on first orders and can move to net terms after a track record.
What is your normal reject rate?
3–5% under 10x loupe inspection for cast and set pieces. Defective units are replaced free in the next shipment.
Where is the factory located?
Wuzhou, Guangxi, China—the core lab-grown and moissanite manufacturing cluster. Shipments go via Guangzhou or Shenzhen ports.
