Alexandrite serves two very different purposes: it’s a rare, color-changing gemstone prized in fine jewelry, and it’s the crystal behind one of the most widely used lasers in dermatology. The gemstone variety can sell for thousands of dollars per carat, while the laser version is a workhorse for hair removal, tattoo removal, and treating skin conditions. Which use matters to you depends on what brought you here, so this guide covers both.
The Gemstone: A Color-Changing Rarity
Alexandrite is a variety of the mineral chrysoberyl that contains trace amounts of chromium. That chromium is what gives the stone its famous trick: it appears emerald green in daylight and shifts to ruby red under incandescent light from candles or tungsten bulbs. The chromium creates an absorption band in the yellow part of the visible light spectrum, which means the stone selectively blocks yellow wavelengths. What’s left for your eye to see is green and red, and which color dominates depends on the light source illuminating it. Daylight is rich in blue-green wavelengths, so the stone looks green. Warm indoor light emphasizes red wavelengths, so the stone turns reddish.
This “emerald by day, ruby by night” effect is extraordinarily rare in nature. Natural alexandrite comes primarily from Russia, Brazil, and Sri Lanka, and high-quality stones are scarce. Top-quality natural gems under one carat average around $1,818 per carat, but stones between one and two carats jump to roughly $6,667 per carat. Larger stones with strong color change command even higher premiums.
Lab-created alexandrite has been available since the 1960s. These synthetic stones are chemically and physically identical to natural ones and still rank among the most expensive synthetic gemstones on the market, though they cost considerably less than their natural counterparts.
Durability for Everyday Wear
Alexandrite rates 8.5 on the Mohs hardness scale, making it harder than nearly every gemstone except diamond (10) and sapphire/ruby (9). It also has excellent toughness and no cleavage, meaning it doesn’t tend to crack or split when struck. According to the Gemological Institute of America, these properties make it a good choice for rings and other jewelry subject to daily wear, including engagement rings.
The Laser: How Alexandrite Works in Medicine
An alexandrite laser uses a synthetic alexandrite crystal to produce light at a wavelength of 755 nanometers. That specific wavelength sits in a sweet spot for targeting melanin, the pigment in skin and hair. When the laser fires, its energy is absorbed by melanin-rich structures while passing through surrounding tissue with minimal damage. This principle, called selective photothermolysis, is what makes the alexandrite laser so useful across multiple dermatological treatments.
Hair Removal
Hair removal is by far the most common use for alexandrite lasers. The 755-nanometer wavelength is absorbed strongly by melanin in hair follicles, heating them enough to destroy the follicular stem cells responsible for regrowth. The laser is widely considered the gold standard for hair removal on lighter skin tones (Fitzpatrick skin types I through III), where the contrast between dark hair and light skin allows the laser to target follicles precisely.
That said, alexandrite lasers aren’t limited to fair skin. A study of 150 patients with darker skin tones (Fitzpatrick types IV through VI) found complications in only 2% of cases across 550 treatment sites, confirming the long-pulsed alexandrite laser is safe for hair removal in darker skin when settings are adjusted appropriately.
A typical course of treatment involves five or more sessions spaced four to six weeks apart, though intervals as short as two or three weeks have shown effectiveness in some studies. The spacing matters because hair grows in cycles, and the laser only works on follicles in their active growth phase. Multiple sessions catch different hairs as they cycle through.
Alexandrite vs. Diode Lasers
The alexandrite laser’s main competitor for hair removal is the diode laser, which operates at a longer wavelength of 810 nanometers. The shorter alexandrite wavelength absorbs melanin more efficiently, which can mean faster results on lighter skin. However, that same strong melanin absorption means a higher risk of heat damage to the surrounding skin, particularly in people with more pigment in their epidermis. Diode lasers penetrate slightly deeper and may require lower energy settings to achieve similar results, which can make them a better fit for medium to dark skin tones. In practice, both technologies are effective, and the choice often comes down to the patient’s skin type and their provider’s experience with each system.
Tattoo Removal
Alexandrite lasers in their Q-switched (short-pulse) form are highly effective for removing certain tattoo colors. The 755-nanometer wavelength works best on black, dark blue, and green inks. Green pigment is particularly notable because it responds poorly to many other laser types but responds well to the alexandrite wavelength. For green tattoos specifically, the Q-switched alexandrite laser is considered the preferred treatment.
Black and dark blue tattoos also respond well to alexandrite lasers, though these colors can be treated effectively by other laser types too. Red, orange, and yellow inks don’t absorb the 755-nanometer wavelength efficiently, so those colors typically require different laser systems.
Treating Skin Conditions
Beyond hair and tattoo removal, the long-pulse alexandrite laser treats several other conditions by targeting either melanin or hemoglobin (the oxygen-carrying molecule in blood that also absorbs this wavelength).
- Pigmented lesions: Dark spots, sun damage, and certain birthmarks contain concentrated melanin that the laser can break down, allowing the body to clear the pigment naturally over the following weeks.
- Vascular lesions: Visible blood vessels near the skin’s surface, such as spider veins, absorb the laser energy through hemoglobin. The heat collapses the vessel walls, and the body gradually reabsorbs the treated vessels.
- Pseudofolliculitis barbae: Commonly called razor bumps, this condition occurs when shaved hairs curl back into the skin and cause inflamed, painful bumps. The alexandrite laser destroys the hair follicles responsible, preventing regrowth and eliminating the source of inflammation.
The laser’s effectiveness on small spider veins and broken capillaries (telangiectasias) is debated and likely depends on the size and type of vessel being treated. Larger or deeper vascular lesions may respond better to other laser wavelengths.
Industrial and Scientific Uses
Outside of medicine and jewelry, synthetic alexandrite crystals serve as the gain medium in tunable solid-state lasers used in research and industrial applications. Because the alexandrite crystal can be tuned across a range of wavelengths (roughly 700 to 820 nanometers), it’s useful in spectroscopy, remote sensing, and other scientific instruments where precise wavelength control matters. These applications are far less visible to the public than the medical and gemological uses, but they represent a meaningful slice of how alexandrite crystals are put to work.