Gemstones are admired for their beauty, rarity, and the enchanting colors they exhibit. Some gemstones, however, possess a remarkable ability to change color under different lighting conditions, adding an element of mystery to their magic. Let’s talk about the fascinating phenomenon of color-changing gemstones, the science behind their color shifts, and the most well-known examples of these captivating stones.
Understanding Color Change in Gemstones
Color change in gemstones is primarily due to the way they interact with light, and the chemical composition of the stone. The phenomenon is most commonly observed in gemstones that contain certain trace elements capable of absorbing different wavelengths of light. When the lighting environment changes, these elements cause the gemstone to reflect different colors.
The Science Behind Color Change
The primary cause of color change in gemstones is the presence of trace elements such as chromium, vanadium, and iron. These elements can alter the way the gemstone absorbs and reflects light. For example, in daylight or fluorescent light, a gemstone might absorb certain wavelengths and reflect others, resulting in a specific color. Under incandescent light, which has a different spectral composition, the gemstone may absorb and reflect light differently, leading to a noticeable color shift.
This phenomenon is known as pleochroism or, more specifically, dichroism or trichroism, depending on whether the gemstone displays two or three different colors. In the case of true color-change gemstones, the color shift is dramatic enough to be easily observed with the naked eye.
Examples of Color-Changing Gemstones
Several gemstones are renowned for their ability to change color. Here are some of the most famous and sought-after examples:
Alexandrite
Alexandrite is perhaps the most famous color-changing gemstone. Discovered in the Ural Mountains of Russia in the 1830s, alexandrite is a variety of chrysoberyl that exhibits a remarkable color change from green in daylight or fluorescent light to red or purplish-red under incandescent light. This dramatic shift is due to the presence of chromium, which causes the gemstone to absorb light differently depending on the light source. High-quality alexandrite, with a pronounced and vivid color change, is extremely rare and valuable.
Garnet
Garnets are typically known for their deep red hues, but certain varieties of garnet can exhibit impressive color changes. Color-change garnets can shift from shades of green, blue, or gray in daylight to red, purple, or pink under incandescent light. This effect is caused by the presence of vanadium and chromium within the gemstone. Color-change garnets are relatively rare and highly prized by collectors.
Sapphire
While blue sapphires are the most well-known, some sapphires exhibit color change as well. Color-change sapphires can transition from blue or violet in daylight to purple or reddish-purple under incandescent light. The color change in sapphires is typically less pronounced than in alexandrite but is still highly valued. These gemstones contain trace amounts of vanadium, which contribute to their color-changing properties.
Spinel
Spinel is another gemstone that can exhibit color change, although it is less common. Color-change spinels can shift from blue or grayish-blue in daylight to purple or pink under incandescent light. This phenomenon occurs due to the presence of trace elements such as iron and chromium. Color-change spinel is prized for its rarity and unique optical properties.
Diaspore (Zultanite)
Diaspore, marketed under the trade name Zultanite, is a gemstone that exhibits a subtle but noticeable color change. Diaspore can shift from a greenish color in daylight to a pinkish-brown or champagne color under incandescent light. The color change in diaspore is due to the presence of trace amounts of chromium and iron. Zultanite is primarily found in Turkey and is valued for its unique and varied hues.
Caring for Color-Change Gemstones
Color-change gemstones, like all precious stones, require proper care to maintain their beauty and optical properties. Here are some tips for caring for these unique gemstones:
Use mild soap and water to clean color-change gemstones. Avoid harsh chemicals and ultrasonic cleaners, as they can damage the stone. Gently scrub with a soft brush and rinse thoroughly.
Store color-change gemstones separately from other jewelry to prevent scratching. Use soft pouches or lined jewelry boxes to protect them from damage.
Be mindful of wearing color-change gemstones during activities that could expose them to hard impacts or abrasive surfaces. Although many of these gemstones are relatively hard, they can still be chipped or scratched.
Have your color-change gemstone jewelry inspected regularly by a professional jeweler. This can help ensure that the settings are secure and the gemstones are free from damage.
Conclusion
Gemstones that can change color offer a unique and captivating feature that adds to their allure and value. The ability to shift hues under different lighting conditions is due to the presence of specific trace elements and their interaction with light. Alexandrite, color-change garnet, sapphire, spinel, and diaspore are some of the most well-known examples of these fascinating gemstones. Proper care and handling can help preserve their beauty and ensure that their magical color-changing properties remain intact for generations to come.
