Crystals and Light • The Fascinating Science

Since the days of Aristotle and Plato right into our modern times, there are lots of theories about crystals and light. But, one thing is for sure, all through the ages and today, everyone absolutely loves crystals.

In fact, the first mention of the use of amulets and talismans goes back to the first days of humankind. Although we have no way of knowing how our ancestors put these items to use, they still hold a strong fascination for many.

Several of these pieces are organic in nature. Explorers found beads made from mammoth ivory in a grave in Sungir, Russia. These beads date back to 60,000 years. The very first historical references of the use of crystals came from the Ancient Sumerian era. There, Ancient Sumerians used them in rituals.

Similarly, Ancient Egyptians used carnelian, clear quartz, lapis lazuli, emerald, and turquoise in their jewelry pieces. The ancient Greeks connected several properties with crystals. In fact, many still use that same knowledge from the Greek era in modern times.

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In ancient China, jade was a highly valued crystal. Several ancient Chinese figures wore jade beads. Interestingly, around 1,000 years ago, musical instruments in China were also made from jade. Jade crystals are a greenish color in the light.

Crystals and Light • The Fascinating Science

What Happens When White Light Hits a Crystal?

When a ray of white light hits a crystal, there occurs a beautiful phenomenon called ‘dispersion of light’. You might also see some rainbow-like occurrences in crystals which happens because of the dispersion of the white light.

Let’s explain this phenomenon in a simpler way! A crystal has several angles inside it. So when a ray of white light passes through it, it has to bend at different angles. That, in turn, causes the white light to split into its seven colors at various frequencies and various angles. The end result is a beautiful rainbow of different colors or simply VIBGYOR (Violet–Indigo–Blue–Green–Yellow–Orange–Red.). All of the colors that your eye detects are the “spectrum of colors“. When white light enters a crystal, the light separates into different wavelengths. The crystal’s internal facets further refract the wavelengths. The overall result is this rainbow spectral-like effect.

Crystals help us understand one fascinating fact about white light.  White light is not actually white.  White light contains within it all the colors of the rainbow.  In fact, according to many scientists, white light contains millions upon millions of colors. The eye can see the VIBGYOR colors, but there are millions of other colors that your eye can not detect.

Reflection & Refraction of Crystals in the Light

Crystals are well-known for their sparkle and brilliance. Their brilliance is an optical property and is directly related to their BRI (Brilliance Refractive Index). BRI involves the bending of white light.  When a crystal is hit by white light, the colors within the ray of light bend at different rates.  This is because each wave of color in the VIBGYOR spectrum travels at a different speed.  Red travels the fastest while, violet travels the slowest.   Due to refraction, the colors bend and exit the crystal at a different angle and even faster speed.  

A crystal’s BRI measurement is based on the refraction of light within a crystal.  This is different from the reflection of light within a crystal. As I’ve stated, the refraction of light within a crystal is the bending of light.  Meanwhile, the reflection of light is when light waves hit an object and do not bend.  Instead, they reflect completely intact. You observe the reflection of light every time you look into a mirror.  Light reflects back at you directly without bending. This is why you see an image of yourself in the same color as on the outside of the mirror.

Reflection and refraction can be observed in crystals because crystals are non-opaque objects.  An opaque object is an object that does not allow waves of light to pass through it.  An object can be opaque because it is too dense for light to pass through. When a ray of white light enters a non-opaque object such as a crystal, the light breaks down into different wavelengths.  The crystal’s internal facets further refract the light. And that is when we finally see the overall result of a rainbow spectral-like effect.

How Do Crystals Get their Colors?

We adore crystals for their beautiful colors, but do you know that these colors are the result of impurities? Usually, the presence of certain minerals in crystals gives them a specific color. For example, the mesmerizing greenish hue of jade is due to chromium and iron impurities.

So, how do these impurities give crystals color when hit by light? The answer is, there are two different chemical structures that give crystals their color: Allochromatic chemical structure and Idiochromatic chemical structure.

The allochromatic chemical structure requires a combination of impurities to achieve its color. For instance, it takes titanium and iron to get blue Safire. Or, as I said before, chromium and iron impurities give jade its greenish. Emerald is produced by chromium and vanadium.

Idiochromatic chemical structure means that its chemical structure is made up of just one element.  For example, the stone Peridot is made green by only one element.  The same is true for emerald and ruby.  They are colored by chromium. 

There is one very important difference between Allochromatic and Idiochromatic chemical structures.  In Allochromatic chemical structures, the impurities which add color are not critical to the structure of the gem. On the other hand, with an Idiochromatic chemical structure, the element is critical to the structure of the gym. This means if you were able to remove that element from the crystal, it would no longer be a crystal. It would be as ordinary, dull, and lifeless as a black, brown, or grey rock.

The Color of Emerald

Similarly, the color of emerald is due to the chromium ion replacing aluminum in certain locations of the structure. Chromium ion gives emerald crystals their beautiful dark-green glow in the light.

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Sapphire’s Sky Blue

Sapphire’s sky blue hue can be attributed to titanium and iron ions replacing aluminum ions in some locations.

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Garnet’s Deep Red

Garnet’s color is due to iron 2+ ions replacing magnesium ions in some locations. Garnet crystal is more complex than other crystals. Most crystals can be identified using their chemical composition. However, Garnets are grouped into two separate “families”: Aluminum Garnets and Calcium garnets. The different chemical compositions within these families are the reason that you can find Garnets in different colors. Deep Red Garnet is in the family of Aluminum Garnets. Yet, they are rarely referred to as Aluminum Garnets.  They are most often identified with a specific location such as the Mozambique garnet. Mozambique garnet has a deeper red than a normal garnet.  Or they will be referred to as “Rhodolite” garnet crystals which have more of a pinkish hue in the light.

In similar ways, the colors of other crystals are either due to impurities or the diffraction of light passing through the crystal structure. Want to know more about these wonderful creations of Mother Nature? Then, I invite you to look below for other fascinating articles in this series.

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