Gemstones are known for their beauty and unique colors. The color of a gemstone is determined by a variety of factors, including selective light absorption. In this blog post, we will explore the role of selective light absorption in gemstone color and how it contributes to the unique characteristics of different types of gemstones.

The Science Behind Selective Light Absorption:

Selective light absorption is a phenomenon where a material absorbs certain wavelengths of light and reflects others. The absorption of light occurs because of the interaction between light and the electrons in the atoms that make up the material. When light passes through a material, it causes the electrons to vibrate. If the energy of the light corresponds to the energy required to excite the electrons to a higher energy level, the light is absorbed. The absorbed energy is then re-emitted as heat or light at a longer wavelength.

The absorption of light is dependent on the chemical composition and crystal structure of the material. Different materials have different electronic structures, which determine the wavelengths of light they can absorb. The crystal structure of a material also affects the way it interacts with light. Some materials have complex crystal structures that cause the absorption of light at specific wavelengths, resulting in unique colors.

Gemstones and Selective Light Absorption:

Gemstones are classified into two categories based on the way they are colored. Type I gemstones are colored by the presence of impurities or trace elements in their crystal structure. Type II gemstones are colored by selective light absorption. Type II gemstones are further divided into two subcategories based on the way they interact with light: those that absorb all visible wavelengths except for one, and those that absorb a range of wavelengths.

One example of a Type II gemstone that absorbs all visible wavelengths except for one is the ruby. Rubies are colored by the presence of chromium in their crystal structure, which causes them to absorb all colors of light except for red. The absorbed light is then re-emitted as red light, resulting in the characteristic deep red color of rubies.

Another example of a Type II gemstone that absorbs a range of wavelengths is the emerald. Emeralds are colored by the presence of chromium and vanadium in their crystal structure. The interaction between the electrons in the crystal structure and the light causes the absorption of light in the blue and yellow parts of the spectrum, resulting in the green color of emeralds.

Factors that Affect Gemstone Color:

Several factors affect the color of gemstones, including the chemical composition, crystal structure, and the presence of impurities or trace elements. For example, the color of diamonds is affected by the presence of nitrogen in their crystal structure. The more nitrogen present, the more yellow the diamond appears. However, if the nitrogen is replaced with boron, the diamond will appear blue.

The crystal structure of a gemstone can also affect its color. Some gemstones, such as tourmaline, have a complex crystal structure that causes them to exhibit multiple colors. The color of tourmaline is determined by the presence of different trace elements and impurities in the crystal structure.

The Importance of Gemstone Color:

Gemstone color has a significant impact on their value and popularity. Certain colors of gemstones are rarer and more valuable than others. For example, a blue diamond is much rarer and more valuable than a yellow diamond.

In addition to their beauty, gemstones also have practical applications. Gemstones are used in scientific and industrial applications, such as laser technology, telecommunications, and medical imaging. The unique properties of each gemstone make them ideal for specific applications.

Enhancing Gemstone Color:

Gemstones can be treated or enhanced to improve their color. Treatments can include heating, irradiation, and diffusion. For example, heat treatment can enhance the color of some gemstones, such as sapphires and rubies, by removing or changing the impurities in the crystal structure. Irradiation can also enhance the color of gemstones, such as diamonds and topaz, by introducing new impurities into the crystal structure. Diffusion treatments involve the introduction of a coloring agent into the surface layer of the gemstone to enhance its color.

While these treatments can improve the appearance of gemstones, there are ethical considerations surrounding their use. Some treatments can be deceptive and misleading to consumers, leading to the sale of falsely advertised gemstones. It is important to purchase gemstones from reputable sources and to be informed about any treatments or enhancements the gemstone has undergone.

Conclusion

Selective light absorption plays a crucial role in determining the color of gemstones. The chemical composition, crystal structure, and the presence of impurities or trace elements all contribute to the unique colors of different types of gemstones. Gemstone color is not only important for its beauty and value, but also for its practical applications in science and industry. While treatments and enhancements can improve the appearance of gemstones, it is important to be aware of any ethical concerns surrounding their use. Overall, the role of selective light absorption in gemstone color is a fascinating topic that highlights the complexity and beauty of the natural world.