Home >> Science & Nature >> Rocks & Minerals

What Is the Rarity of a Diamond?

Diamonds are one the rarest of the precious gemstones and, consequently, one of the most expensive. The formation of diamonds began very early in Earth's history when extreme temperatures and pressures created ideal conditions for compressing carbon. Diamonds come in many shapes and sizes, and there are four qualities that determine the rarity and value of a particular gem. These are known as the Four C's: carat weight, color, clarity and cut.

Carat Weight
- Larger diamonds are more rare than small diamonds.
  
  Because diamonds are formed so deep beneath the Earth's surface, very few actually make the treacherous journey to where humans can mine them. Because of this, the larger the diamond, the more rare it is. Diamond size is measured using metric carats, where one carat weighs about 0.2 grams. The carat is divided into 100 points because even the smallest fraction of a difference in weight can have a big impact on the value of the diamond. However, even two diamonds of equal weight can have drastically different values depending on their other characteristics.
Color
- Color is an important quality in determining the rarity of a diamond.
  
  In the gemstone industry, diamonds that approach colorlessness are considered rare. The Gemological Institute of America (GIA) has created a scale to measure the color of diamonds to very subtle differences, often not even detectable by those without specific tools or training. The exceptions to the rule of less color are the fancy color diamonds, so called because they occur with natural hues of blue, brown or pink. These diamonds are even more rare than the colorless variety. According to the GIA, for every naturally tinted diamond, there are approximately 10,000 colorless stones that make it to the Earth's surface.
Clarity
- The clarity of diamonds has to do with inclusions, which are internal imperfections, and blemishes, which are external imperfections caused by the process of rising through the Earth's crust. Diamonds with fewer of these so-called "birthmarks" are more rare, and are more valuable. The GIA Clarity Scale describes 11 types of diamonds when magnified 10 times, ranging from flawless to imperfect. Flawless diamonds are exceptionally rare.
Cut
- Diamond ore underoges a process of cutting and polishing that can also greatly impect a diamond's rarity.
  
  The cut of a diamond is perhaps the most difficult quality to analyze. Appraisers look at three attributes in determining the rarity of a diamond's cut: its brightness, which indicates how much light is reflected off the surface; its fire, which shows the dispersion of the reflected light into the color spectrum; and its scintillation, which is basically how it sparkles. In terms of rarity, the shape of the diamond's cut refers to proportions, symmetry and polish. The standard diamond shape is called round brilliant, and all other shapes, such as emerald cut, marquee, pear, oval and heart shapes, are known as fancy cuts.

Rocks & Minerals