Rainbow diamonds, also known as fancy color diamonds, refer to naturally colored diamonds that exhibit multiple colors. While most diamonds appear colorless or with a slight yellowish tint, rainbow diamonds display a spectrum of vibrant hues within a single stone. So what causes the rainbow effect in these rare and beautiful diamonds? Are rainbow diamonds simply a marketing gimmick or do they really exist in nature? Let’s take a closer look at how rainbow diamonds form and the factors that contribute to their magical multicolored appearance.
What causes the rainbow color in diamonds?
In simple terms, the rainbow color phenomenon in diamonds is caused by structural imperfections and mineral impurities present within the diamond crystal during formation. Interestingly, the defects and inclusions that give rise to the rainbow effect are extremely rare, making up less than 0.1% of all naturally occurring diamonds.
First, we need to understand the typical composition of a diamond. Diamonds are crystallized forms of pure carbon that develop when carbon atoms bond tightly together under intense heat and pressure deep within the Earth’s mantle. This dense crystalline structure enables diamonds to refract light so effectively that colorless diamonds appear transparent with a brilliant shine.
Rainbow diamonds form when this crystalline lattice structure becomes deformed by irregularities. Structural defects like twinning, stress planes, or mosaic structures within the diamond disrupt light refraction and cause it to diffuse into the different colors of the spectrum. Additionally, the presence of trace mineral impurities like nitrogen, boron or hydrogen can influence areas of crystal growth and also lead to light dispersion.
The specific colors exhibited depend on the type and orientation of these inclusions. For instance, blue and pink diamonds get their color from the presence of boron atoms. Green and red diamonds occur when crystal irregularities are oriented to reflect those light wavelengths. So in essence, the rainbow effect stems from a unique combination of structural anomalies and mineral deposits that collectively diffract white light into an array of rainbow colors.
What are the characteristics of rainbow diamonds?
Rainbow diamonds display a wide range of characteristics depending on the nature of their inclusions and how the colors manifest. Here are some of the key features that identify these rare multicolored diamonds:
- Display multiple colors such as red, orange, yellow, green, blue, purple, pink, etc.
- Colors are naturally occurring and not induced by artificial treatment.
- Pattern of colors may be distributed, graduated, concentrated or discrete.
- Degree of color saturation can range from faint to intensely vivid.
- May exhibit changing color distribution in different lighting.
- Usually contain inclusions and irregular crystal structures.
- Colors originate within the diamond, not on the surface.
- Retain their rainbow color and do not fade over time.
No two rainbow diamonds are exactly alike when it comes to the precise blend and patterning of rainbow hues. The colors can appear as discrete blotches, taper into gradients, branch like dendrites or swirl together in abstract patterns. This one-of-a-kind coloration is why each rainbow diamond is considered a truly unique jewel of nature.
How rare and valuable are rainbow diamonds?
Natural rainbow diamonds are exceptionally rare. Among all diamonds sourced worldwide, only about 1 in 10,000 display any color, and rainbow diamonds make up a tiny fraction of those. The Gemological Institute of America estimates that fewer than 0.1% of all diamonds exhibit the rainbow effect to some degree. This scarcity places rainbow diamonds in the top echelon of precious colored diamonds.
The market value of rainbow diamonds is determined by many factors, including:
- Intensity of saturation – Vivid colors are more valued than pale hues
- Number of primary colors – Diamonds with 5+ colors have premium value
- Pattern and distribution – Solid bands and sharp color changes raise value
- Diamond cut and clarity – Well-cut, clean stones are most desirable
- Carat weight – Larger rainbow diamonds are exponentially rarer
Based on these criteria, prices can range dramatically from around $5,000 per carat into the millions for rare specimens weighing over 5 carats. In 2017, a 13.9 carat vivid rainbow diamond sold for a record $31.1 million at auction – over $2 million per carat. While not all rainbow diamonds command such astronomical prices, they remain some of the most coveted and expensive diamonds in the world.
Where do natural rainbow diamonds come from?
Rainbow diamonds originate from the same ultra-deep diamond mines that produce colorless diamonds. These special diamond deposits exist in vertical volcanic shafts known as kimberlite pipes. Diamonds form under intense heat and pressure around 140 to 190 kilometers (87 to 118 miles) below the Earth’s crust and are carried to the surface in molten rock eruptions millions of years ago.
Most of the world’s natural rainbow diamonds historically came from two sources:
- Golconda in India – The historic Golconda mines were known for phenomenally large diamonds, many exhibiting exotic colors.
- Premier Mine in South Africa – This mine yielded rare fancy vivid yellows, pinks, blues, and rainbows over its lifespan.
Today, Australia is emerging as a new hotspot. The Argyle Mine, before its closure in 2020, was renowned as the world’s primary source of pink, red and chameleon diamonds. As mining companies gain access to previously unreachable depths, more rainbow diamond deposits may be uncovered worldwide.
Can rainbow diamonds be created synthetically?
It is possible to create synthetic diamonds with rainbow colors in a lab, but they remain distinctly different from their exceptionally rare natural counterparts. There are two main methods used to produce synthetic rainbow diamonds:
- HPHT – Simulating the conditions under which natural diamonds form using high pressure and heat to grow synthetic diamond crystals.
- CVD – Depositing carbon vapor onto a diamond seed crystal to build rainbow layers synthetically.
However, human-made rainbow diamonds tend to have a more uniform, repetitive banded pattern that is visibly distinguishable from the organic flair of natural rainbow diamonds. Synthetic production also cannot recreate the exceptional clarity and crystalline perfection only achieved by diamonds formed in nature. That is why natural rainbow diamonds are still the most treasured despite advances in synthetic diamond technology.
How are rainbow diamonds authenticated?
Distinguishing natural rainbow diamonds from lab-grown simulants relies on advanced gemological testing and expert evaluation. Some of the techniques used to authenticate include:
- Microscopy – Checking for natural growth structures and irregular diamond graining.
- Spectroscopy – Detecting natural inclusions and mineral composition.
- Fluorescence – Most synthetics have stronger UV fluorescence.
- EDXRF – Analyzing minor element impurities absorbed during natural formation.
- Photoluminescence – Natural diamonds emit different light signatures.
Diamond grading reports from respected labs like GIA and GCAL provide documentation of authenticity for natural rainbow diamonds. Reputable jewelers will only sell verified natural rainbow diamonds that come with grading reports to prove their precious rarity and value.
Notable examples of rainbow diamonds
Some of the most famous rainbow diamonds ever discovered include:
| Diamond | Carat Weight | Color Profile |
|---|---|---|
| Moussaieff Red | 5.11 | Vivid red, purple, pink, orange, yellow |
| Graff Vivid Pink | 5.00 | Pink, purple, violet, blue, yellow |
| Love Light | 5.03 | Orangy pink, purplish pink, violet, blue, green |
These one-of-a-kind rainbow diamonds showcase the breathtaking range of colors and patterns that can occur naturally in these extremely rare gems. They exemplify why natural rainbow diamonds are regarded as the pinnacle of the colored diamond world.
Conclusion
In summary, rainbow diamonds do exist in nature but they are extraordinarily rare and valuable. Their magical array of colors arises from unique structural irregularities and mineral traces that occur during the diamond’s formation within the Earth. Rainbow diamonds display an endless variety of color combinations and patterns, making each one a truly mesmerizing miracle of nature. Synthetic production methods have not been able to replicate the intricate beauty of these natural rainbow diamonds – proving that the best diamonds still come from nature alone.
