Dark Area in Loose Diamond

When examining a diamond, one should always check for dark areas marring the brilliance and clarity of the stone. Dark areas can be the result of imprecise cutting that produces poor symmetry, or they can arise from natural causes. Usually dark areas lower the value of the diamond.

The Bow Tie Effect

• Dark areas often look like a bow tie. page boy with bow-tie, smiling image by Jane September from Fotolia.com

  Many dark areas in diamonds have the shape of a man's bow tie, hence the term "bow tie effect." The bow tie effect occurs when the diamond has not been cut optimally, causing asymmetry and dark areas. The areas sometimes look glassy or watery rather than clear and light-reflective.

Carbon Spots

• Carbon spots often look like ground pepper. Condiment/ container of salt & black pepper image by L. Shat from Fotolia.com

  Carbon spots are small spots on a diamond that appear similar to ground black pepper. Diamond experts at Van Diamond write, "Inclusions in a diamond are usually not carbon but other minerals---olivine being the most common---carbon spots are very rare and not really noticeable as easy-to-see spots."

Removing Dark Areas

• Diamond dealers can remove carbon spots through laser drilling, but the process can make the stone more fragile and easily breakable. In most diamonds the bow tie effect is irreversible.