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Glossary for Custom Gemstone Cutting – Key Terms

Updated: Feb 18, 2021

Embracing the art of custom gemstone cutting in Sri Lanka? It can be confusing to a novice. To help with the terms that may sound jargon to you, we are readying a glossary with the key terms you’ll encounter.

Brilliance – This refers to the light reflected from the interior of a gem. Factors such as the gem’s reflective index, design proportions, polish and the clarity of the material affects its brilliance. Diamond, sphene, zircon, garnet, sapphire, and ruby are some of the gemstones that are usually cut to maximize its brilliance.

Caliper – This is a device used to measure the dimensions of a gemstone.

Carat – Often confused with karat that’s used to measure the purity of gold, or carrot, an orange root vegetable, this Carat refers to a unit of weight specifically for gems. One unit of carat is equal to 200 milligrams or 1/5 of a gram. Each carat is subdivided into 100 ‘points’ for precise measurements to the hundredth decimal place.

Carat ScaleA carat scale is a device used to measure the weight of a gemstone.

Cleavage, Fracture and Parting – These terms refer to how mineral stones break when they are put under stress. If a crystal under stress breaks and forms a smooth plane or crystal shape, it is referred to as cleavage. Parting, on the other hand, is uncommon and often confused with cleavage. In the event of a break, if fracture marks on a cleavage or an outline of a crystal etched in a mineral are found, it is considered to be a parting. A fracture is more common and happens when a mineral chips or breaks along an uneven or irregular surface.

Colored Stones – Colored stones are any gemstone that isn’t a diamond. It is a common term used to identify both precious and semi-precious stones.

Cutter, Polisher or Faceter – A cutter is someone who cuts and polishes faceting designs on a diamond while a faceter is someone who cuts and polishes faceting designs on colored stones.

Dispersion of Light – Gemstones are widely known for their prism-like reflection of light. As light is passed through some varieties, it tends to bend and split or disperse into a spectacular spectrum of colors. Diamonds are famed for their dispersion in multiple colors. Rutile and cerussite are two other gemstones that have an even greater dispersion effect.

Eye Clear or Eye Clean – Eye Clear or Eye Clean is a grading given to a gemstone that has no imperfections visible to the naked eye. However, they are not flawless (FL) or internally flawless (IF) stones. The imperfections present are simply not easy to detect. Therefore, they still offer excellent value and command a higher price.

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