Turquoise, a captivating gemstone admired for its vibrant blue-green hues, has been cherished by cultures around the world for centuries. However, over time, turquoise can undergo a transformation and turn green instead. This phenomenon has puzzled gem enthusiasts and scientists alike. In this article, we will delve into the science behind why turquoise changes color, exploring factors such as oxidation, light exposure, and chemical alterations.
The Chemistry of Turquoise:
Turquoise is primarily composed of hydrated copper aluminum phosphate. Its distinctive blue-green color is attributed to the presence of copper ions within its crystal lattice structure. When pure, turquoise exhibits a beautiful blue hue. However, various factors can influence its color alteration, leading to a shift towards green tones.
Oxidation:
One prominent reason for turquoise turning green is oxidation. Copper, an essential component of turquoise’s color, is susceptible to oxidation when exposed to oxygen and other environmental elements. Over time, this oxidation process causes the copper ions in the turquoise to change, resulting in a shift towards green shades. Additionally, the presence of iron impurities can further contribute to the color change.
Light Exposure:
Another significant factor that can cause turquoise to turn green is excessive exposure to light. Natural sunlight and ultraviolet (UV) radiation can initiate photochemical reactions within the gemstone. These reactions can alter the electron structure of the copper ions, leading to a change in their absorption properties. As a result, turquoise may lose its blue hues and adopt a greener appearance.
Chemical Alterations:
Turquoise can also undergo chemical alterations due to external factors, leading to a change in its color. Exposure to certain chemicals, such as cosmetics, perfumes, and household cleaning agents, can cause chemical reactions with the gemstone. These reactions can damage the crystal lattice structure and modify the arrangement of copper ions, resulting in a shift towards green tones.
Environmental Factors:
The environment in which turquoise is stored or worn can significantly impact its color transformation. High humidity levels and exposure to moisture can accelerate the oxidation process within the gemstone, leading to a faster change from blue to green. Similarly, storing turquoise in areas with high levels of sulfur or hydrogen sulfide, such as near hot springs or volcanic regions, can cause chemical reactions that alter its color.
Treatment and Stabilization Techniques:
In the gem industry, certain treatment and stabilization techniques are employed to enhance and preserve the color of turquoise. These techniques involve impregnating the gemstone with various resins or waxes to prevent oxidation and maintain its vibrant blue hues. However, it’s important to note that treated turquoise may still undergo color changes over time, albeit at a slower rate compared to untreated stones.
Care and Maintenance:
To minimize the risk of turquoise turning green, proper care and maintenance are essential. Here are a few tips to help preserve the color of your turquoise jewelry:
Avoid prolonged exposure to sunlight and UV radiation.
Store turquoise away from chemicals and harsh cleaning agents.
Remove turquoise jewelry before swimming, showering, or engaging in activities that may expose it to excessive moisture.
Clean turquoise gently using a soft cloth and mild soapy water. Avoid abrasive cleaners or brushes that could damage the gemstone’s surface.
Conclusion:
Turquoise, renowned for its alluring blue-green hues, occasionally undergoes a color transformation and turns green. The change is primarily attributed to oxidation, light exposure, and chemical alterations. Understanding these factors can help us appreciate the dynamic nature of this gemstone while also providing insights into how we can preserve its vivid colors. By practicing proper care and maintenance, we can prolong the life and beauty of turquoise jewelry, ensuring it continues to captivate us for generations to come.
