Diamond's characteristic chemical composition and crystal structure make it a unique member of the mineral kingdom.
Diamond is the only gem made of a single element: It is typically about 99.95 percent carbon. The other 0.05 percent can include one or more trace elements, which are atoms that aren't part of the diamond's essential chemistry. Some trace elements can influence its color or crystal shape.
The way a mineral forms helps determine its identity. Diamond forms under high temperature and pressure conditions that exist only within a specific depth range (about 100 miles) beneath the earth's surface. Diamond's crystal structure is isometric, which means the carbon atoms are bonded in essentially the same way in all directions. Another mineral, graphite, also contains only carbon, but its formation process and crystal structure are very different. The result is that graphite is so soft that you can write with it, while diamond is so hard that you can only scratch it with another diamond.
A diamond has to go through a lot before it reaches the jeweler's display case. It forms deep in the earth under extreme heat and pressure. It's ejected violently upward until it arrives at or near the earth's surface. It's forced from its hiding place by nature or by man. Then it's cleaved and cut and polished until its natural beauty shines through.
Without any one of these factors, diamond might be just another mineral. Fortunately, though, this special combination of chemical composition, crystal structure, and formation process gives diamonds the qualities that make them extraordinary.
On almost all modern birthstone lists, diamond is recognized today as the birthstone for April. Diamond is also the gem that marks the 60th and 75th wedding anniversaries.
Legend & Lore
Diamonds have a long history as beautiful objects of desire. In the first century AD, the Roman naturalist Pliny stated: "Diamond is the most valuable, not only of precious stones, but of all things in this world."
The world's love of diamonds had its start in India, where diamonds were gathered from the country's rivers and streams. Some historians estimate that India was trading in diamonds as early as the fourth century BC. The country's resources yielded limited quantities for an equally limited market: India's very wealthy classes. Gradually, though, this changed. Indian diamonds found their way, along with other exotic merchandise, to Western Europe in the caravans that traveled to Venice's medieval markets. By the 1400s, diamonds were becoming fashionable accessories for Europe's elite.
In the early 1700s, as India's diamond supplies began to decline, Brazil emerged as an important source. Diamonds were discovered in the pans of gold miners as they sifted through the gravels of local rivers. Once it reached its full potential, Brazil dominated the diamond market for more than 150 years.
The 1800s brought increasing affluence to western Europe and the United States. Explorers unearthed the first great South African diamond deposits in the late 1800s just as diamond demand broadened. The story of the modern diamond market really begins on the African continent, with the 1866 discovery of diamonds in Kimberley, South Africa. The South African sources affected many segments of the diamond industry. This was especially true as diamond mining moved from the surface to farther underground. Because of the huge costs and comparatively low yields involved, the new sources forced the development of more efficient mining techniques. They created the need for better marketing. They also led to advances in cutting and polishing—advances that increased efficiency, reduced costs, and enhanced the appearance of finished stones.
In the 1870s, annual production of rough diamond was well under a million carats. By the 1920s, the figure was around three million carats. Fifty years later, annual production approached 50 million carats, and in the 1990s it surpassed 100 million carats per year.
One of the first things most people learn about diamonds is that not all diamonds are created equal. In fact, every diamond is unique. Diamonds come in many sizes, shapes, colors, and with various internal characteristics.
Jewelry professionals use a systematic way to evaluate and discuss these factors. Otherwise, there would be no way to compare one diamond to another. And there would be no way to evaluate and discuss the qualities of an individual diamond. Diamond professionals use the grading system developed by GIA in the 1950s, which established the use of four important factors to describe and classify diamonds: Clarity, Color, Cut, and Carat Weight.
These are known as the Four Cs. When used together, they describe the quality of a finished diamond. The value of a finished diamond is based on this combination.
Diamonds come in many colors. Diamonds that range from colorless to light yellow and brown fall within the normal color range. Within that range, colorless diamonds are the most rare, so they're the most valuable. They set the standard for grading and pricing other diamonds in the normal color range.
The GIA D-to-Z scale is the industry standard for color-grading diamonds. Each letter represents a range of color based on a diamond's tone and saturation.
Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they're called clarity characteristics. Clarity is the relative absence of inclusions and blemishes.
Like the rest of the Four Cs, clarity's influence on value is directly related to the concept of rarity. Flawless is the top grade in the GIA Clarity Grading System. Diamonds graded Flawless don't have visible inclusions or blemishes when examined under 10-power (10X) magnification by a skilled and experienced grader. Flawless diamonds are very rare. They're so rare, in fact, that it's possible to spend a lifetime in the jewelry industry without ever seeing one, and they command top prices.
At the other end of the scale are diamonds with inclusions that can be easily seen by the unaided eye. Between the two extremes are diamonds with inclusions visible only under 10X magnification. Diamonds in the middle range make up the bulk of the retail market.
There are 11 clarity grades in the GIA clarity grading system. They are Flawless, Internally Flawless, two categories of Very, Very Slightly Included, two categories of Slightly Included, and three categories of Included.
The effect of a clarity characteristic on the clarity grade is based on its size, number, position, nature, and color or relief.
A beautiful diamond looks the way it does because of three optical effects: white light reflections called brightness; flashes of color called fire; and areas of light and dark called scintillation. Pattern is the relative size, arrangement, and contrast of bright and dark areas that result from a diamond's internal and external reflections. There must be enough contrast between the bright and dark areas to give the pattern a crisp, sharp look.
The term "cut" also can describe a fashioned diamond's shape. Shapes other than the standard round brilliant are called fancy cuts. They're sometimes called fancy shapes or fancies. Fancy shapes also have names of their own, based on their shapes. Some of the best known are the marquise, princess, pear, oval, heart, and emerald cut.
Diamond weights are stated in metric carats, abbreviated "ct." One metric carat is two-tenths (0.2) of a gram—just over seven thousandths (0.007) of an ounce. One ounce contains almost 142 carats. A small paper clip weighs about a carat.
The metric carat is divided into 100 points. A point is one hundredth of a carat.
Diamonds are weighed to a thousandth (0.001) of a carat and then rounded to the nearest hundredth, or point. Fractions of a carat can mean price differences of hundreds—even thousands—of dollars, depending on diamond quality.
Over a carat, diamond weights are usually expressed in carats and decimals. A 1.03-carat stone, for example, would be described as "one point oh three carats," or "one oh three." Weights for diamonds that weigh under a carat are usually stated in points. A diamond that weighs 0.83 carat is said to weigh "eighty-three points," or called an "eighty-three pointer."
Diamonds in the normal color range are colorless through light yellow and are described using the industry's D-to-Z color-grading scale. Fancy color diamonds, on the other hand, are yellow and brown diamonds that exhibit color beyond the Z range, or diamonds that exhibit any other color face-up. These rare specimens come in every color of the spectrum, including, most importantly, blue, green, pink, and red.
Diamonds can be cleaned safely with lint-free cloths, commercial jewelry cleaning solutions, and household detergents.
Harsher cleaning methods are not recommended for home use. These include powdered abrasive household cleansers, ultrasonic cleaners, and steam cleaners.
This information was excerpted from GIA's Gem Encyclopedia with permission from GIA.