Color plays a crucial role in determining the value and identity of gemstones, but have you ever wondered why gemstones have such vibrant colors? How do gemstones get their color? The answer is more complex than you might think.
How Do We Perceive Color?
Let’s start by understanding how we perceive color.
Our eyes are truly remarkable. When light enters the eye, it passes through the pupil and reaches the retina, where photoreceptors are triggered. These photoreceptors send electrical signals to the brain, which decodes the signals, allowing us to see.
There are two main types of photoreceptors: rods and cones. Rods are sensitive to low light and help with peripheral vision, while cones, located in the center of the retina, provide detailed vision and color perception.
What Color Actually Is?
Now that we know how we see color, let’s explore what color actually is.
Cones detect different wavelengths of light, and these wavelengths are responsible for the colors we see. The range of wavelengths that humans can see falls between approximately 400 and 700 nanometers, which we call the visible light spectrum.
Different animals have different numbers of cone cells, affecting their ability to perceive colors.
Dogs, for example, have two types of cone cells, allowing them to see fewer colors than humans, while bees have four types, enabling them to see more colors. Mantis shrimp take it to another level with an astounding 12 different types of cone cells, allowing them to see a broad spectrum, including infrared and ultraviolet light.
When white light, composed of all the wavelengths in the visible light spectrum, interacts with objects such as grass, birds, or rough gemstones, some wavelengths are absorbed, others are transmitted, and some are reflected back. The wavelengths that reflect and enter your eye inform your cones about the colors you perceive.
For instance, green light bouncing off leaves tells your brain that they are green, while brown hair reflects a different combination of wavelengths. In essence, color is the modification of white light. Objects that appear black absorb a wide range of wavelengths, while objects that appear white reflect most of the wavelengths. This explains why a black car gets hotter in the sun compared to a white car—it absorbs more energy.
Why Are Rubies Red? Why Are Emeralds Green?
Now let’s tackle the million-dollar question: why are rubies red and why are emeralds green? How do gemstones get their color?
Understanding the coloration of gemstones takes us deeper into the complexities of color. Similar to other colored objects, gemstones absorb specific wavelengths of light while reflecting others.
In gemstones, transition elements often play a crucial role in their coloration. For instance, titanium or cobalt can create a blue color, chromium can cause red or green, and copper is responsible for the captivating blue hues of turquoise.
The color of some gemstones is determined by their fundamental chemical composition. These gems, known as idiochromatic or self-coloring gems, rely on specific elements within their chemical makeup to exhibit their characteristic color.
For example, malachite without copper would cease to be malachite. On the other hand, allochromatic gems derive their color from trace elements that are not essential to their chemical composition. The presence of these coloring agents, considered impurities, adds a delightful array of colors to the gemstone.
Take ruby, for instance, with a chemical composition of Al2O3; it’s the presence of chromium that imparts its stunning red color. Sapphire, also composed of Al2O3, derives its color from iron and titanium.
If you think your mind is already blown, consider gems that showcase color change. These gems display different hues depending on the temperature of light. The most famous example is alexandrite, which reflects both red and blue portions of the visible light spectrum.
When exposed to warmer light, it appears red, while cooler light causes it to exhibit a bluish-green hue. Naturally, the explanation behind these phenomena is far more intricate, and while the principle of transition elements offers a foundation for understanding color causes, the underlying subatomic mechanisms are still largely theoretical.
Nonetheless, what remains consistent is that incoming wavelengths of light provide energy that is absorbed, and the wavelengths reflected in your eye determine the color of the stone.
Transition elements are not the sole contributors to gemstone color.
Defects or vacancies in the crystal structure can also impact how we perceive a gem’s color. Additionally, colorful optical effects such as iridescence can arise from the gem’s structure.
Opal, for instance, consists of stacked silica spheres whose size and arrangement influence how light interacts within the stone. As light passes through and between these spheres, diffraction, and interference occur, resulting in the mesmerizing play of rainbow colors that opal is renowned for.
How do gemstones get their color? To recap, three elements are required to perceive color in gemstones: light, a gemstone of your choosing, and at least one keen eye. Oh, and the more cone cells, the better! Speaking of cones, have you ever wondered what the vision of a mantis shrimp is like?
Conclusion On How do gemstones get their color
Hope this post about how do gemstones get their color may help you out. Whether it’s through the presence of transition elements, trace impurities, or defects in the crystal structure, gemstones absorb and reflect specific wavelengths of light to create their unique colors.