|Color||Colorless, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black|
|Refractive Index||2.417 - 2.419|
|SG||3.1 - 3.5|
|Cleavage||1, all sides - octahedral. Dodecahedral Diamonds and Borts exhibit poor cleavage or no cleavage at all.|
Diamonds have been known and treasured as gemstones since ancient times. However, their only significant source was in a limited supply in the alluvial river deposits of India. Small amounts of Diamonds were also found in Brazil in the 1700's, but it wasn't until the 1870's that the vast Diamond fields of South Africa were discovered and exploited. Since that time, many new significant worldwide deposits have been discovered, and since then the popularity of Diamond has grown tremendously due to increased supply and technological advances in cutting.
The most typical color used for Diamond jewelry is colorless. However, most Diamonds have a light tint, usually yellowish or brownish. Perfectly clear Diamonds are much more valuable than their lightly tinted counterparts. Although light yellow tinting is frowned on, a deep yellow color renders the Diamond as a fancy. Fancy yellow Diamonds have recently increased in popularity in jewelry. "Fancy", the term used to describe any deeply colored Diamond, not only includes the more common yellows and browns, but it also is used to describe the very rare tones of red, pink, purple, blue, and green. Black Diamonds, which are more common and less expensive, are occasionally faceted as opaque yet shiny gems. (For additional information on fancy Diamonds, please visit our Colored Diamond Shoppers Guide and our article titled "How are Natural Fancy Colored Diamonds Created".)
Roughly twenty percent of Diamonds mined are used in jewelry, as most are unsuitable for gemstone use. The vast majority are either opaque and not gem quality, or are too heavily flawed. A flawless Diamond is exceptional, as most Diamonds gemstones contain some level of flaws, even if they are very minute.
The immense hardness of Diamond contributes to its suitability and importance as a gemstone. Because of its hardness, a Diamond is immune to scratching, as the only thing that can scratch it is another Diamond. This resistance lends it the ability to withstand daily wear and tear beyond the capabilities of most gemstones. Diamonds are also difficult to polish due to their hardness - they can only be polished with special Diamond saws that have a thin layer of Diamond on the saw blades and edges.
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Diamond is the most important gemstone in the jewelry industry. The colorless stone is most often used for jewelry, although yellows and browns are also used. (Brown stones are often marketed as "chocolate", "cognac", or"champagne" Diamonds, depending on color depth). Other fancies are too rare and expensive for the mainstream jewelry industry, and are exclusively reserved for the high end consumer. Black, opaque Diamonds are occasionally faceted into a black gemstones with a submetallic luster.