Last updated on November 23, 2022
Diamond blemishes are clarity characteristics that can appear during the cutting, setting and wearing of a diamond. Their size, quantity and placement, along with diamond inclusions, determine a stone’s clarity grade and affect its price. This guide brings together types of diamond blemishes to give you an idea of what they mean and how they affect a stone.
What Are Diamond Blemishes?
Diamond blemishes are external clarity characteristics that occur on a polished diamond’s surface. They can appear during the cutting and setting processes as well as from the wearing and improper storage of a finished stone.
Diamond blemishes include abrasion, burn marks, extra facet, lizard skin, natural, nick, pit, polish lines, rough girdle, scratches and surface graining. Often these flaws can be polished down or can be cut to remove.
The number of blemishes, along with their size and placement, can detract from the diamond’s appearance, making it look dull and lifeless, influencing its clarity grade. However, some blemishes are so minute that they are virtually invisible to the naked eye and are only seen under 10x magnification.
Types of Diamond Blemishes
Abrasion
Abrasion is a series of tiny nicks along a facet junction on a polished diamond. This type of blemish gives a stone’s edges a milky and fuzzy appearance. It usually occurs as a result of careless handling.
Burn Marks
Burn marks refer to the hazy area on a diamond’s surface caused by excessive heat coming off the polishing wheel when a diamond is polished too rapidly. These cloudy areas can usually be polished out without affecting the stone’s durability.
Extra Facet
As the name suggests, an extra facet is an additional facet introduced during the manufacturing process not required by the cutting style. Extra facets are usually found near the girdle and are commonly used to polish out a natural or a nick. They affect the diamond’s symmetry but are not considered in clarity grade evaluation. That is why diamonds with the highest clarity grades often have extra facets to polish away the inclusions and blemishes.
Lizard Skin
Lizard skin is a type of diamond blemish that looks like a wavy or bumpy area on a polished diamond. It appears during the manufacturing process when a stone gets polished in the wrong direction. The lizard skin effect can easily be polished out without affecting a diamond’s durability.
Natural
Natural is a portion of a rough diamond left unpolished on a finished stone usually found on or near the girdle.
Nick
A nick is a tiny chip on a facet junction commonly found on the girdle or culet. They are usually a result of careless wearing and can weaken the diamond’s structure by extending to additional fractures from the base of the cavity if hit hard.
Pit
A pit is a tiny cavity on a polished diamond that looks like a white dot. This clarity characteristic usually results when diamond polishers extract pinpoints during the polishing process.
Polish Lines
The term “polish lines” refers to thin parallel grooves and ridges that occur on a facet but do not cross a facet junction. They are either transparent or white and are caused during the polishing process.
Rough Girdle
A rough girdle specifies an irregular or granular girdle surface. It is usually accompanied by feathering or bearding and can be a sign of a diamond’s durability issue.
Scratch
A scratch is a thin white line across the diamond’s surface. It can appear during the handling, mounting or wearing of a diamond.
Surface Graining
The term “surface graining” refers to small lines, angles and curves caused by irregularities in crystal growth. Unlike internal graining, surface graining appears on the surface of a diamond. Surface grain lines are commonly invisible to the naked eye and usually have minor importance.
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