Loose Diamonds with higher clarity grades are more valued, with the exceedingly rare "flawless" graded diamond fetching the highest price. A clarity grade is assigned based on the overall appearance of the stone. Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. However, large clouds can affect a diamond's ability to transmit and scatter light.
Large cracks close to or breaking the surface may reduce a diamond's resistance to fracture. Loose Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal defects of a diamond called inclusions, and surface defects called blemishes. Clarity is one of the four Cs of diamond grading, the others being carat, color, and cut. Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond.
However, minor inclusions or blemishes are sometimes considered to have some value, as they can be used as unique identifying marks analogous to fingerprints. In addition, as synthetic diamond technology improves and distinguishing between natural and synthetic diamonds becomes more difficult, inclusions or blemishes can be used as proof of natural origin. The diamond was used in two ways-for decorative purposes, and as a talisman to ward off evil or provide protection in battle. The diamond was also used for some time as medical aid.
Diamonds were also ingested in the hope of curing sickness. Due to the heightened public awareness of the value of loose diamonds, mine owners perpetuated myths that diamonds were poisonous. This was to prevent the mineworkers swallowing the diamonds in an attempt to smuggle them out of the mines.