Diamonds are universally acknowledged as one of the hardest substances on earth. In fact, this knowledge is so common, the word “diamond” comes from the Greek word “adámas” for unbreakable. Throughout history, diamonds have been used as tools for cutting and engraving, starting with their discovery in India around the 9th century BCE. Because diamonds are so hard to even scratch, they were left in their raw, natural form for millennia. They were only being used as icons for luck, prosperity, and wealth when not in use as tools.
Diamonds wouldn’t be used in jewelry until 1074, when the first diamond in any accessory was used in a crown for a Hungarian Queen.
Today, diamonds are just as common worn as beautifully cut and polished jewelry. When most people think of diamonds, they think of the classic clear, “white” diamond. This type of diamond is considered “pure” because the only element in the crystal is carbon. Technically speaking, diamonds have the same chemical make up as the graphite in #2 pencils. What gives almost all gemstones their color is the impurities found in the crystal structure. For example, chromium impurities in corundum makes red sapphires, or rubies.
Unlike most gemstones, diamonds only get their color from three sources: boron (blue), hydrogen (purple), and nitrogen (brown to yellow). From most common to most rare, the colors diamonds can be are: brown, clear/white, blue, green, black, pink, orange, purple/violet, and red.
Brown, Orange, & Yellow
As nitrogen is a fairly common element, it makes up the majority of our air (about 70%), it’s the most common impurity in diamonds. Brown, orange, and yellow diamonds are actually more common than clear diamonds.
Boron isn’t as common as nitrogen, but you probably have it in your home. It’s one of the main ingredients in Borax and how the powder got its name. Blue diamonds get their color from trace amounts of boron in the crystal, with higher amounts leading to darker, more saturated hues.
Green diamonds are different from the others because they’re not actually green. Certain things appear to be certain colors by which type and how much light they reflect. White appears white because all the light is being reflected, black appears black because all the light is being absorbed. White light can be broken up by a prism, or diamond, to show the entire rainbow. So, it makes sense that if something is green, it’s because green light is being reflected. It’s why plants appear green. Green diamonds do the same thing.
Diamonds are formed deep underground, where there’s a lot of pressure and heat. They are brought to the surface by volcanic magma, flowing like a river from deep in the Earth’s mantle to the upper crust. Just as the diamonds reach the surface, they can be exposed to naturally occurring radiation. This radiation doesn’t always affect the diamond, but it can cause certain mutations. After being exposed, the diamond will absorb more red and yellow light than a normal clear one, making it look green.
Black diamonds aren’t actually black. They don’t have impurities in them, either. A “black” diamond is pure carbon, like a clear one, but the crystal isn’t perfect. In the diamond are bits of graphite, giving it it’s black color. Black diamonds, or carbonados, are actually the toughest of all naturally occurring diamonds.
Pink & Red
Pink and red diamonds aren’t actually pink or red, either. Like black diamonds, they get their color from their structure not being quite so perfect. Like green diamonds, they “get” their color by absorbing certain colors of light. While they’re still deep in the Earth’s crust, the heat and pressure cause the perfect diamond structure to shift and distort. This distortion allows them to absorb green light, appearing pink. Red diamonds, the rarest color, get their color this way.
Purple diamonds are strange. They’re strange in that, though they’re not as rare as some other colors, true purple diamonds are hard to find. Most purple diamonds have a secondary color, like brown or red, as an overtone. This way, the diamond will appear brownish-purple instead of a true purple or violet.