Alexandrite is a type of gemstone known for its ability to change color under different lighting conditions. The color change effect is caused by the presence of trace amounts of various elements in the gemstone’s chemical composition.

One of the key elements responsible for alexandrite’s color change is chromium. When light is absorbed by the gemstone, the chromium ions in the crystal lattice become excited and emit green fluorescence. This causes the gemstone to appear green in natural sunlight or incandescent light.

However, when alexandrite is exposed to fluorescent light, the chromium ions are not as strongly excited, and the gemstone appears red or purplish-red in color. This color change effect is known as the “alexandrite effect,” and is caused by the interaction of the gemstone’s chemical composition with different lighting conditions.

In addition to chromium, alexandrite may also contain other trace elements, such as vanadium and titanium, which can affect the gemstone’s color. These elements can cause alexandrite to appear yellow, brown, or gray in different lighting conditions, in addition to the typical green and red colors.

The color change effect of alexandrite is highly valued by gem collectors and is considered a rare and desirable quality in a gemstone. As a result, alexandrite is often used in high-end jewelry and can command high prices.

Overall, alexandrite’s ability to change color is a unique and fascinating property of the gemstone, and is caused by the presence of various elements in its chemical composition. This color change effect is highly prized by gem collectors and is a defining characteristic of alexandrite.