What are Color-Change Gemstones?

Written By Allie Perry February 21, 2025

My second job ever in the jewelry industry was at a small shop that did repairs for local jewelry stores. If you dropped your ring or necklace off at one of these chain stores to be sized or fixed, there was a good chance it came to me to do that actual work.

I had a formal education in jewelry and silversmithing, and I’d spent a few years working in mass production, but I was new to repair. I learned a lot on the job, and my boss, Ken, let me learn some things all on my own.

One of the most memorable of these lessons came from an alexandrite ring. I can’t remember, decades later, what the ring was actually in the shop for…perhaps just a sizing. But I distinctly remember sitting at my bench and admiring the stunning green stone, twinkling in the natural light streaming through the windows.

The work I did in that shop was done in batches. It’s still how I like to approach work today- size all the rings at once, solder all the chains, do whatever repair needs to be done at the bench, and save them all to be polished in one big batch at the end of the day. Polishing jewelry is the most satisfying part of a repair job, since it brings the piece back to new; but it’s also the dirtiest. Scrubbing that dirty polishing compound off of my hands and arms, and out from under my fingernails, was something I didn’t care to do more than once a day if I could avoid it.

There were days when I did dozens of repairs, and days when I did hundreds, and my focus wasn’t on the style or the stones, but rather the repair itself. I wanted to make sure I did the repair completely and correctly, and polished the piece fully so that any work I’d done was invisible. I didn’t memorize each piece. Sometimes I knew I’d sized a ring or fixed an earring, but didn’t exactly remember the size or shape of the stones in the piece.

On that day I’d admired the beautiful green alexandrite on my bench, I took my ready-to-be-polished batch of jewelry to the next room, away from the natural daylight and into the incandescent lighting of the polishing machine, and started polishing everything…only to find that the beautiful green stone was now…purple?

What?

Was I remembering things correctly?

I paused for a moment and recalled the Pink Sapphire Incident at that same job.

My boss had given me a pink sapphire ring that needed to be repaired. I think it needed to have a prong retipped. Even with my limited repair experience, I know some stones could safely withstand the heat needed for soldering or other tasks, and others could not. I asked if it was safe to do the job with the stone in place. He said yes, so off to the bench I went.

I cleaned the ring, set the repair up, lit my torch and got to work. Retipping a prong requires adding metal to the top of an existing prong that’s worn down to the point of being unsafe for the security of the stone. I prepared a piece of gold and soldered it in place on the worn part of the prong…only to discover the pink stone was no longer pink, and the color had completely vanished. 

It was one of those moments when you feel you heart fall right through your stomach and straight out of your butt.

The benches in that shop were set up in such a way that my boss sat right behind me, and could see over or around my shoulder if he wanted to keep an eye on what I was doing. I thought surely he’d watched me destroy this stone and I’d be in a bunch of trouble, if he let me continue to work there at all.

I sat still for a second. Think. Don’t panic. THINK. What did I know about pink sapphires? Not enough!

While I sat there contemplating my imminent dismissal from this job I loved so much, magic happened before my very eyes. As the stone air-cooled, the pink settled back in. But for my rapidly thumping heart, there was no evidence it had changed at all.

It was at that moment I heard a giggle from behind me. Ken had known all along that the stone would change color under the heat of the repair and then slowly change back, damage free, and he’d let me sweat it out while I learned that lesson in the most nerve-wracking way possible!

So was this once-green-now-purple stone another lesson from Ken?

I picked up the ring and peeked my head around the corner to show it to him so I could ask if I’d slowly gone insane without anyone noticing. Lo and behold, the ring I held out to show him once again had a green stone!

My baffled expression elicited another giggle from Ken and he told me all about color-change stones like the alexandrite I was holding in my confused hand. I was fascinated, and then relieved, and then fascinated again to learn about these rare stones.

What Are Color-Change Gemstones?

Color-change gemstones exhibit a dramatic shift in color when viewed under different types of lighting, typically daylight and incandescent light. That’s why I saw a green stone at my workbench and a purple stone at the polishing machine. This crazy phenomenon occurs due to the stone’s unique interaction with light wavelengths, specifically how the crystal structure absorbs and reflects them under varying conditions.

What Are Some Types of Color-Change Gemstones?

Alexandrite

One of the most famous and valuable color-change gemstones is alexandrite. It’s a variety of chrysoberyl that shifts from greenish-blue in daylight to reddish-purple under incandescent light. Natural Alexandrite is rare, and very valuable depending on the strength and clarity of the color shift. Lab-created alexandrite is a good substitute for you if. You want the bod color change of alexandrite without the hefty price tag.

Color-Change Sapphire

Unlike traditional blue sapphires, color-change sapphires exhibit a shift from blue or violet in daylight to purplish or reddish hues in incandescent light. This effect is caused by the presence of trace elements such as vanadium in the crystal structure. Color-change sapphire are very rare, and in my twenty-five years in the field, I’ve never seen one in person.

Chameleon Diamonds

Chameleon diamonds can change color, but their shift happens a little bit differently than color-change gemstones. They’ll turn from a stable yellowish-green to yellow if you keep them in the dark for at least 24 hours! You can also view the color change if you heat them to the right temperature. But bring it back into the light or remove the heat, and that yellow color reverts back to the yellowish-green. And there are some chameleon diamonds that do the exact opposite-they start out yellow and turn green only when heated- and they display no color-change in light. There are famous examples of color-change diamonds that change color with a simple change of light source. Either way, chameleon diamonds are extremely rare.

Garnet

While garnets are often associated with deep reds, some varieties, such as color-change garnet, display remarkable shift through many colors- bluish green to purple, reddish brown to reddish purple or pink, reds to oranges- all by simply viewing them under incandescent light. Many color-change garnets will even exhibit a third color under candle light. The most. Common color-change varieties of garnet are pyrope or spessartite.

Diaspore

Diaspore is a lesser-known but stunning color-change gemstone that can shift from kiwi green in daylight to champagne tones or even pinkish hues under incandescent lighting. If you’ve ever heard of Zultanate or Csarite, these are trademarked varieties of diaspore that typically display dramatic color changes.

This list isn’t exhaustive, with other color-change stones like topaz, spinel, or fluorite. And while some stones display vibrant color shifts in their natural state, others have their color-shifts enhanced by heating, irradiation, or exposure to certain wavelengths of UV light.

Why Do These Gemstones Change Color?

The color change in these gemstones occurs due to their specific chemical composition and how they interact with light. Science! Certain elements within the crystal, such as chromium, vanadium, or iron, absorb different wavelengths of light depending on the source. In natural daylight, which is rich in blue wavelengths, the stone may appear green or blue. Under incandescent light, which is warmer and contains more red wavelengths, the stone reflects those hues instead.

Are Color-Change Gemstones Rare and Valuable?

The value of a color-change gemstone depends on several factors, including the intensity and quality of the color change, the size and clarity of the stone, and its overall rarity. Alexandrite is considered one of the most expensive color-change stones due to its strong color shift and scarcity. Color-change garnets are valuable, though generally more affordable than alexandrite. Zultanite is a more recent discovery and is increasing in popularity, adding to its growing market value.

How Do I Care for Color-Change Gemstones?

In short, you can care for them in similar ways to most other fine gemstones.

• Avoid harsh chemicals: Many gemstones are sensitive to acids and cleaning agents. Use mild soap and water with a soft brush for cleaning.
• Store separately: Color-change stones should be stored separately from other jewelry to prevent scratching or damage.
• Limit exposure to extreme heat and light: Some gemstones may experience fading or changes in their properties when exposed to prolonged heat or UV light.
• Regular professional check-ups: If set in jewelry, periodic inspections by a jeweler can ensure that the settings remain secure and that the stone remains undamaged.

If you’re ever unsure about how you should care for your color-change gemstone jewelry, you can always reach out to a reputable jeweler for guidance.

And while color-change gemstones can be slightly alarming if you’re a new repair-jeweler who doesn’t know they exist, they’re really a marvel of nature. If you’re looking for a one-of-a-kind piece of jewelry that will constantly surprise and delight, a piece with a color-change gemstone is the perfect choice!