The Chameleon Gemstone: Color-Changing Alexandrite

Alexandrite is a gemstone known for it's incredible chameleon-like color-changing properties. Nicknamed the "emerald by day, ruby by night," alexandrite shifts between shades of green, blue, purple, and red depending on the light. So, why does alexandrite change color? This remarkable color shift is caused by two different phenomena: the alexandrite effect and pleochroism.

The Alexandrite Effect

Objects in our world appear different colors based on how they absorb and reflect light. If something appears red, it is absorbing all the blue, green, yellow, and other colors in the spectrum, while reflecting or scattering red light to your eyes. In the same way, the way a gemstone absorbs and scatters light will affect the color it appears. So what determines how a gemstone absorbs light and what color it displays? This is determined by the trace elements, or impurities, within the atomic structure of the stone. Different elements absorb and scatter different colors of light.

One specific trace element that is found in alexandrite is mostly responsible for its drastic color-changing properties, and that element is chromium. Chromium ions are really good at absorbing yellow and dark blue light, and not so good at absorbing red, green, and lighter blue light. This is why alexandrite appears more red in warm lighting - warm lighting has more red light (and not much blue and green light), so the gemstone reflects or scatters the red light, giving the stone a red or purple appearance. In regular daylight, there is more blue and green light, so the stone scatters this blue or green light.

Another color-changing effect that chromium provides can be seen when exposed to long wave or short wave ultraviolet light, or black light. When exposed to this UV light, alexandrite glows a neon red. This is because when chromium ions absorb UV light, it causes the electrons of the chromium to get excited and bounce up and back down between energy levels. As these electrons bounce back down in energy levels, they shed energy which manifests in the form of light. This fluoresence will appear stronger in stones with more chromium. Most natural alexandrites don't display fluorescence as strongly as lab-grown alexandrites, because lab-grown alexandrites are typically higher in chromium.


The second, completely different phenomenon that causes color change in alexandrite is called "pleochroism." Pleochroism is a term used to describe stones that appear multiple different colors based on the angle light enters a stone. Meaning if you look at a stone from different angles, it can appear different colors. Depending on the angle, alexandrite can appear green, blue, or red. While this may sound very similar to the alexandrite effect, there is a big difference - pleochroism refers to a stone appearing different colors based on the angle it is viewed, while the alexandrite effect refers to a stone appearing different colors based on different lighting conditions.

Choosing a Color-Changing Alexandrite Ring

Alexandrite is an excellent center stone for use in engagement rings - not only is it one of the birthstones for June, but it is very durable sitting at an 8.5 out of 10 on the Moh's Scale of Hardness. However, when choosing alexandrite for your choice of center stone for an engagement ring, it must be noted that each stone varies in color and appearance based on how much chromium and other trace elements are in the stone, the lighting the stone is exposed to, the cut of the stone, etc.

At Staghead Designs, we almost always work with lab-grown alexandrite unless specifically requested otherwise, as natural Earth-mined alexandrite is incredibly rare and expensive. While the more cost-effective lab-grown alexandrite is grown in a controlled lab, they still can vary greatly in color! In choosing an alexandrite center stone, you should know that your stone can appear anywhere in a spectrum of colors between blue, teal, purple, or red and that your stone will likely appear different colors in different lighting. This is simply the nature of the stone! If you prefer a gemstone that is a specific color all the time, we recommend checking out other unique gemstone options like sapphire, moissanite, or garnet.

Check out our collection of alexandrite engagement rings, or work with our designers to design your dream alexandrite wedding ring today!