Glossary
Gemological Terms & Definitions
A comprehensive guide to understanding gemological terminology used in diamond, gemstone, and jewelry certification.
A series of minute scratches or nicks on the surface of a gemstone, typically found along facet junctions. Abrasions can affect the overall appearance and clarity grade of a stone.
The total amount of light reflected from a diamond or gemstone back to the viewer. Brilliance is one of the key factors in determining a stone's beauty and value, along with fire and scintillation.
The standard unit of weight for gemstones, equal to 200 milligrams or 0.2 grams. One carat is divided into 100 points, so a 0.50 carat diamond is also referred to as a 50-point stone.
The assessment of internal and external characteristics (inclusions and blemishes) in a diamond or gemstone. Clarity grades range from Flawless (FL) to Included (I) for diamonds, indicating the relative absence of these characteristics.
A crystalline form of carbon that is the hardest known natural material. Diamonds are valued based on the 4Cs: Cut, Color, Clarity, and Carat weight. Natural diamonds form deep within the Earth under extreme pressure and temperature.
Any treatment or process applied to a gemstone to improve its appearance, durability, or value. Common enhancements include heat treatment, irradiation, and fracture filling. AIG reports clearly disclose all enhancements.
A flat, polished surface on a cut gemstone. The number, size, and arrangement of facets determine the stone's cut quality and how it reflects light, affecting its brilliance and fire.
The dispersion of white light into spectral colors, creating flashes of color in a diamond or gemstone. Fire is one of the three main optical effects, along with brilliance and scintillation, that contribute to a stone's beauty.
A professional who studies, identifies, and evaluates gemstones. Gemologists use specialized knowledge and equipment to determine a stone's identity, quality, and authenticity. AIG employs world-renowned gemologists with extensive training and experience.
A measure of a gemstone's resistance to scratching, measured on the Mohs scale from 1 (softest) to 10 (hardest). Diamond is the hardest at 10, while talc is the softest at 1. Hardness affects a stone's durability and suitability for jewelry.
Internal characteristics within a gemstone, such as crystals, clouds, feathers, or other materials. Inclusions are natural features that can help identify a stone's origin and affect its clarity grade. They are often visible under magnification.
A diamond created in a laboratory using advanced technology that replicates the natural diamond formation process. Lab-grown diamonds have the same physical, chemical, and optical properties as natural diamonds but are created in weeks rather than millions of years.
Small diamonds or gemstones, typically weighing less than 0.18 carats (about 3.5mm in diameter). Melee stones are often used as accent stones in jewelry settings. AIG provides specialized bulk and melee services for these smaller stones.
A gemstone that formed naturally in the Earth through geological processes over millions of years, without human intervention. Natural gemstones are distinguished from synthetic or lab-grown stones in AIG reports.
The quality of the surface finish on a gemstone's facets. Polish is one of the factors evaluated in cut grading, ranging from Excellent to Poor. Good polish allows maximum light reflection and enhances a stone's brilliance.
A comprehensive document issued by a gemological laboratory that details the characteristics, quality, and authenticity of a gemstone or piece of jewelry. AIG reports include identification, grading, measurements, and can be verified online using a unique report number.
The sparkle or flash of light seen when a diamond or gemstone moves. Scintillation is caused by the reflection of light from the stone's facets and is one of the three main optical effects that contribute to a gemstone's beauty.
A gemstone created in a laboratory that has the same chemical composition, crystal structure, and physical properties as its natural counterpart. Synthetic gemstones are man-made and should be clearly identified as such in gemological reports.
Any process applied to a gemstone to enhance its appearance or durability. Common treatments include heat treatment, irradiation, fracture filling, and coating. AIG thoroughly tests for and clearly discloses all treatments in our reports.
The process of confirming the authenticity of a gemological report by checking the unique report number through AIG's online verification system. This ensures that the report is genuine and has not been altered or counterfeited.
The four main characteristics used to evaluate and grade diamonds: Cut (the quality of the stone's proportions and finish), Color (the presence or absence of color), Clarity (the presence of inclusions and blemishes), and Carat (the weight). These criteria form the standard for diamond grading worldwide.