Because diamonds form under tremendous heat and pressure, nearly every one possesses internal and external features called clarity characteristics. These characteristics help gemologists separate natural diamonds from synthetics and simulants, as well as identify individual gems.
In the first of a two part series, we explore a diamond’s internal characteristics or those that extend into the diamond from its surface – these are called diamond inclusions. (Next time we’ll cover external characteristics, or blemishes.) A GIA Diamond Grading Report provides a diagram that uses symbols to illustrate the position of a diamond’s inclusions. We’ve listed diamond inclusions commonly found in diamonds with brief explanations. Enjoy!
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Bearded Girdle Very small feathers that extend from the girdle surface into the stone; can result from the cutting process. |
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Bruise A tiny area of impact accompanied by very small, root-link feathers; typically occurs at a facet junction. Courtesy of Gary Roskin, G.G., F.G.A. |
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Cavity An angular opening created when part of a feather breaks away or when a surface-reaching crystal drops out or is forced out during polishing. |
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Chip A shallow opening caused by damage to the stone’s surface that typically occurs at a girdle edge, facet junction, or culet. |
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Cloud Many tightly grouped pinpoints that might be too small to distinguish individually but together have a hazy appearance. |
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Crystal A mineral crystal contained in a diamond. |
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Feather General trade term for a break in a gemstone, often white and feathery in appearance. |
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Grain Center A small, concentrated area of crystal distortion; can be white or dark, and might have a thread-like or pinpoint-like appearance. |
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Indented Natural A portion of the rough diamond’s original surface that dips below a polished diamond’s surface. |
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Internal Graining Lines, angles, or curves that might appear whitish, colored, or reflective, or affect transparency at 10X; caused by irregularities in crystal growth. |
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Internal Laser Drilling Laser drilling within a diamond that creates a surface-reaching feather, or expands a pre-existing feather around a dark inclusion so that it reaches the surface. The feather then provides access for bleaching to decrease the visibility of the inclusion. |
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Knot A white or transparent diamond crystal that extends to the surface after fashioning. |
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Laser Drill-hole A tiny, surface-reaching tunnel produced by a laser light beam. |
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Needle A thin, elongated crystal that looks like a tiny rod at 10X. |
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Pinpoint A very small crystal that looks like a tiny dot at 10X. |
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Twinning Wisp A series of pinpoints, clouds, or crystals that forms in a diamond’s growth place; associated with crystal distortion and twinning planes. |
All images are magnified to provide you with closer detail. If you want to see a larger version of the inclusion, click the image. Just don’t expect all clarity characteristics to look exactly like these pictures!
