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The Science Behind Diamond Color Creation
Diamonds aren’t naturally colorless at all – that’s just a popular myth. A chemically pure and structurally perfect diamond would indeed be transparent with no hue, but almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond is actually affected by chemical impurities or structural defects in the crystal lattice. It’s like nature’s own chemistry set working deep underground, where tiny imperfections become the source of breathtaking beauty.
Think about this incredible fact: only about 1 in 10,000 natural gem quality diamonds is fancy colored. Similarly, only 1 in every 10,000 diamonds possess natural color, and the more intense the color, the rarer and more valuable the diamond. What makes these diamonds so special isn’t what they lack, but what tiny amounts of foreign elements and structural changes they’ve acquired during their billion-year journey to our hands.
Yellow Diamonds – The Golden Performers
The presence of nitrogen causes a diamond to appear yellow, with the intensity of the yellow color dependent upon varying amounts of nitrogen. Type I diamonds have nitrogen atoms as the main impurity, commonly at a concentration of 0.1%, and if nitrogen atoms are dispersed throughout the crystal in isolated sites, they give the stone an intense yellow or occasionally brown tint. This is why yellow diamonds are sometimes called “canary diamonds” in the jewelry world.
For 2024, yellow diamonds remain the most popular fancy diamond color and are also known as canary diamonds. Nitrogen gives these gems their vivid yellow color, making for sunny and eye-catching jewelry. Natural yellow diamonds are incredibly rare, with color intensity ranging from light yellow to darker coloration. The nitrogen atoms essentially act like tiny filters, absorbing blue light and allowing the warmer yellow tones to dominate what we see.
Blue Diamonds – The Boron Beauties
The presence of boron impurities is often responsible for the color of natural blue diamonds, with more boron creating deeper blue. Fancy blue diamonds are very rare in nature, and boron in a diamond primarily absorbs yellow light. When that yellow is canceled out, it permits us to see the blue wavelengths. It’s fascinating how such tiny amounts of an element can create such dramatic visual effects.
The color blue comes from the chemical element boron trapped inside the diamond. Although blue diamonds only need a tiny amount of boron to produce their color, they are extremely rare, with only one in 200,000 natural diamonds showing a light shade of blue and even fewer displaying a deep, rich color. India was historically the source for blue diamonds, though within the last several years, notable blue diamonds have been found at the Cullinan Mine in South Africa.
Pink and Red Diamonds – The Mystery Colors
While the color of most natural diamonds can be scientifically explained, the origin of pink coloration in diamonds still puzzles scientists. They believe that pink diamond shades are caused by plastic deformation, in response to extreme natural stresses during the diamond’s storage deep below the surface of the earth. This means that they didn’t actually start their growth process pink, making pink one of the rarest fancy colored diamonds.
The red color of the graining in fancy red diamonds from Brazil is caused by absorption related to the 550 nm band. This band, the most common cause of pink to red color in natural, untreated diamonds, is thought to be the result of a defect created by plastic deformation. Red diamonds are the rarest and therefore the most expensive of all natural colored diamonds. Although still uncertain, scientists believe that red diamonds get their color the same way as pink diamonds, because of plastic deformation. Red natural diamonds are so rare that only around twenty to thirty are known to exist in the entire world and most are less than half a carat in size.
Green Diamonds – The Radiation Result
Green diamonds get their color when radiation displaces carbon atoms from their normal positions in the crystal structure. This can happen naturally when diamond deposits lie near radioactive rocks, or artificially as a result of treatment by irradiation. Naturally colored green diamonds are extremely rare. A natural green diamond’s color does not develop until the end of their journey to the earth’s surface. The color comes from natural irradiation, usually caused by alpha particles. Absorbing red and yellow light causes the diamond to reflect a green hue, however this is usually confined to a very thin layer at the surface of the original rough diamond so it’s very rare that the green color will be present throughout the diamond. Only a handful of green diamonds come to market each year.
What makes green diamonds particularly intriguing is their origin story. Unlike other colored diamonds that get their hues from chemical impurities during formation, green diamonds develop their color through a completely different process involving natural radioactivity in the earth.
Brown Diamonds – The Common Beauties
Brown diamonds are the most common natural color in diamonds. Their color is caused by either structural defects in the diamond lattice or traces of nitrogen within the diamond lattice. This means that along with yellow diamonds, they are the only colored diamonds whose color is graded on the normal diamond color scale. Once relegated to industrial use, brown diamonds gained cachet in the 1980s when marketers gave them romantic names like champagne, cognac and chocolate. The color in natural brown diamonds is caused by internal parallel brown grain lines due to distortion of the crystal lattice. Brown diamonds are generally more affordable compared to other fancy colors.
The transformation of brown diamonds from industrial stones to desirable gems shows how marketing and perception can completely change the value of natural resources. Today’s “chocolate diamonds” were yesterday’s industrial-grade stones.
Black Diamonds – The Inclusion Champions
Most naturally colored black diamonds get their color from large quantities or clouds of minute mineral inclusions such as graphite, pyrite or hematite that extend throughout the stone. These diamonds may also have numerous cleavages or fractures that are stained black or have become black because of graphitization. Concentrations of these internal features are responsible for the coloration. However, the actual body color of a natural black diamond may range from near-colorless to brown or “olive” green.
Black diamonds are not truly black. They contain numerous dark inclusions, meaning little light can pass through them, so this is what gives them their dark appearance. While other colored diamonds are transparent, the many inclusions in a natural black diamond means it is typically opaque and they will not exhibit the same fire and brilliance of a colorless or transparent colored diamond. Black diamonds are the toughest of all the different natural diamond colors.
Orange Diamonds – The Nitrogen Masters
Natural yellow gem diamonds are the most common of the fancy-color diamonds, while orange diamonds are among the rarest when they have unmodified hues. Both categories owe their coloration to atomic-level lattice defects associated with nitrogen impurities in the diamond structure. Four major groups of defects are responsible for the color in nearly all yellow and orange diamonds: cape defects, isolated nitrogen defects, the 480 nm visible absorption band, and H3 defects.
Based on a decade of GIA data, the broad absorption is responsible for the color in roughly 5% of yellow diamonds. Among diamonds with orange hue components, the 480 nm band is the second most common cause of color. However, for diamonds with pure unmodified orange hues, this feature is responsible for the color in roughly 86% of these ultra-rare and highly valued stones. The 480 nanometer absorption band creates some of the most sought-after orange diamonds in existence.
Purple Diamonds – The Hydrogen Mystery
It may surprise you to know there is not a decisive explanation for what causes us to see purple in natural diamonds. Hydrogen or boron can be present, just as with blue or gray, but we suspect that extremes of pressure also compressed the crystal lattice in a way that causes the blue or gray transmission to change to purple. Whenever you see a purple diamond you can tell your friends that the reason behind its color remains one of the very few unsolved mysteries of the gemological world.
Purple diamonds are caused by a combination of crystal lattice distortion and high hydrogen content. The exact mechanism behind purple coloration represents one of the remaining puzzles in diamond science, making these stones not just beautiful but scientifically fascinating as well.
Gray Diamonds – The Hydrogen Effect
We see gray due to the presence of hydrogen, or sometimes boron. And speaking of boron, one of the rarest and most valuable natural diamond colors is also caused by boron. Gray diamonds often serve as stepping stones between colorless and more intensely colored varieties, showing how subtle changes in impurity concentrations can create distinctly different appearances.
Gray diamonds demonstrate the delicate balance in nature’s color-creation process. Just slight variations in hydrogen or boron content can shift a diamond from one color category to another, highlighting the precision required in natural diamond formation.
The Rarity Factor and Market Values
The incredible rarity of popular colored diamond shades makes these gems especially valuable. Natural colored diamonds have the greatest value of all, with fancy colored lab diamonds typically having lower price tags than their natural counterparts. Red diamonds are the most expensive of the fancy colored diamonds. In 2023 and 2024, diamond prices declined significantly, mainly due to economic downturns and the rising popularity of lab-grown diamonds. However, this decline is considered temporary, presenting an opportunity for buyers. Meanwhile, prices for investment-grade diamonds have remained relatively stable due to their scarcity and enduring demand.
The market reflects nature’s own economics – the rarer the natural process that creates a particular color, the higher the value collectors and jewelry enthusiasts place on those stones.
Crystal Lattice Defects and Color Science
Imperfections in the crystal lattice of diamond are common. Such defects may be the result of lattice irregularities or extrinsic substitutional or interstitial impurities, introduced during or after the diamond growth. The defects affect the material properties of diamond and determine to which type a diamond is assigned; the most dramatic effects are on the diamond color and electrical conductivity.
Point defects encompass those defects which are “point-like”, and which typically can be described within only one or two diamond unit cells, with fewer than ten atoms deviating significantly from the perfect, pure-carbon diamond structure. Extended defects include crystallographic faults such as dislocations and very large defect aggregates such as interstitial or vacancy clusters. So-called optical defects cause absorption in the visible or near-visible portions of the electromagnetic spectrum, often producing coloration. Luminescence reactions result when defects absorb higher-energy incident radiation and then reemit lower-energy radiation as visible light. Optical defects occur in very low concentrations in all diamonds, and their presence can be detected using spectroscopic techniques.
Modern Detection and Classification Methods
In a laboratory setting, the identification of diamonds is based mainly on the detection of tiny imperfections in the atomic lattice. These “defect centers” may include foreign impurity atoms, carbon atom vacancies in the lattice, carbon atoms positioned in between normal lattice locations, and dislocations where planes of carbon atoms are offset from one another. Not all of these lattice imperfections create spectroscopic features, but several do so by allowing the diamond to absorb particular energies of incident light or radiation. Defects can occur randomly or in particular locations within the lattice. Diamonds can contain more than one type of defect, and in natural diamonds, defects can be altered over geologic time in the earth or by exposure to heat or radiation during color treatment.
Today’s gemological laboratories use sophisticated spectroscopic equipment to identify the exact cause of each diamond’s color, helping distinguish natural stones from treated or synthetic alternatives.
Time and Temperature’s Role in Color Development
Nitrogen-bearing diamonds are thought to incorporate isolated nitrogen during growth by substitution for carbon, meaning that natural diamonds start out with yellow to orange color. However, only the very rare type Ib diamonds maintain that original color. With time at high temperatures deep in the earth, the nitrogen atoms in most diamonds aggregate, resulting in either near-colorless stones or yellow diamonds colored by cape defects.
Much like colorless diamonds, colored diamonds were formed between 900 million to 3.2 billion years ago, deep below the earth’s surface, under intense heat and extreme pressure. They too are made up almost entirely of carbon atoms, however low levels of foreign atoms per million carbon atoms or structural defects can change them from colorless to colored. The incredible timescales involved in diamond formation mean that colors can evolve over geological time periods, with nitrogen atoms migrating and clustering in different patterns.
The Future of Colored Diamond Understanding
While many color-producing defects can be introduced through laboratory treatment processes, atomic level distortions in a diamond’s crystal structure created by plastic deformation cannot. We know that plastic deformation is associated with the vast majority of diamonds with these colors, but we still do not know the actual atomic structure of the defect causing the color. The researchers said that there is no known method of replicating plastic deformation with the 550 nm absorption band by a laboratory treatment or growth process.
Science continues advancing our understanding of these natural marvels. The exact details of how these factors combine to produce red color are still being studied, and ongoing research continues to deepen our understanding of this complex process. It’s worth noting that the coloration of diamonds, especially rare and vivid hues like red, is a combination of intricate geological and chemical factors that occur over millions of years during the diamond’s formation deep within the Earth’s mantle. As technology and scientific techniques advance, we may gain further insights into the precise mechanisms behind the formation of red diamonds and their unique coloration. What started as mysterious colored stones are gradually revealing their atomic-level secrets, making each discovery more fascinating than the last.
