Feathers are a very common type of inclusion in a diamond and are generally easy to spot. Sometimes they are transparent but usually they are milky white or light brown to grayish in color. A feather is a natural internal fracture or cleavage, depending on which direction it follows in the crystal. It is usually associated with inherent stress in the diamond. Cleavage feathers will parallel one of the eight possible octahedral faces and if breaking the surface, they will be flat and sometimes facet-like in appearance. Fracture feathers run parallel to a single grain, which divides the octahedral faces. When these open up to the surface, they are step-like and rough or jagged in appearance.
Feathers can be especially hazardous when close to the girdle surface and/or brownish in color. When asking your setter to hide one of these feathers under a prong, ask him to proceed with great caution. Sometimes with a sharp blow, pressure from a cutter’s wheel or a stone setter’s push, feathers can travel making them larger in appearance.
Named after the appearance of a bird’s feathers, they can be so tiny that they will often look like scratches on the surface (sometimes referred to as hairline feathers). The larger the feather, the more likely it will affect the durability of the diamond. In selling highly imperfect stones, a dealer runs the risk of unhappy returning customers with feathers that have fallen out or opened up to the surface in their diamond. Of course when dealing with the trade, the buyer must be aware of such potential hazards or eventually he’ll run into problems.