Diamond and Gemstone Glossary
Diamond and Gemstone Glossary
Adularescence: refers to the appearance of a floating light in cabochon gemstones such as moonstone.
Altered Stone: any gemstone that has been altered through an enhancement process.
Anatomy: a set of characteristics that every diamond possesses after it has been cut and polished.
Angle of Incidence: an angle at which light enters a gemstone.
Appraisal: documents some key characteristics of a diamond. These characteristics include: carat weight, cut, color, clarity, and measurements.
Asscher Cut: similar to the emerald cut but with higher crown and larger step facets.
Asterism: the appearance of a star in the gemstone caused by the reflection of light from and inclusion.
Balas Rudy: Red Spinel.
Baroque: may refer to a gemstone or a pearl with an irregular shape.
Baton: also known as baguette cut.
Bead Setting: a method of securing a faceted gemstone in a setting.
Bezel: a thin ring of metal used to secure a gemstone instead of prongs.
Biaxial: A gemstones which has two distinct optic axes.
Blemish: A blemish is an external flaw on the surface of the diamond. Although some blemishes are naturally occurring, most are sustained during the unearthing, cutting, polishing, or all of the above.
Bearding (“girdle fencing” or “dig marks): bearding occurs around diamonds’s girdle as the stone is being cut. Bearding presents as fine lines and can resemble a single strand of human hair. Usually bearding isn’t a problem, however excessive bearding can diminish the luster of the stone.
Blocking: the process of placing facets on a gemstone.
Blood Diamond: refers to diamonds that could have been used to fund conflicts.
Bow Tie: an effect that is commonly found in marquise, oval, and pear, and radiant shaped diamonds that resembles a bow tie.
Brilliance: is the term used to describe the radiance / brightness of a diamond.
Brilliant Cut: A cut specifically designed to maximize brilliance of a diamond. In this cut, all facets radiate out from the center of the diamond towards the edges. Some of the most popular brilliant cuts include: round, oval, and princess cut diamonds.
Bruise: a chip on the surface of diamond.
Cabochon: a gemstone with a smooth, domed form.
Carat: The term Carat comes from the use of carob beans by merchants to measure the weight of gemstones during the days of early gem trade. A Carat is a unit of weight. One carat is equal to 0.2 grams.
Carbons: are a small, black spots of carbon that may be present in a diamond. These flaws can effect clarity.
Cavity: a depression on the surface of a diamond.
Certification: a process by which a diamond is certified and graded by an independent laboratory such as GIA
Chips: breaking off of a small piece of diamond from the surface of the stone. Chips usually occur from environmental stress.
Chive: a gemstone with a concave depression
Clarity: clarity of a diamond is directly related to the degree at which inclusions and blemishes are present. Diamonds with the least amount of imperfections are valued higher than those with a greater degree of inclusions and blemishes.
Cleavage: straight cracks that occur in a diamond parallel to the crystallographic planes. Cleavages usually the result of strain or a strong blow delivered to the stone. Diamond with cleavages should be avoided for jewelry purposes as they are relatively easy to break.
Clouds: three or more inclusions present close to one another are referred to as a cloud. These inclusions can cause a dark or cloudy spot in the stone.
Coated Stone: A gemstone treated with a transparent coating to enhance color.
Color Grading: a system of grading the color of a diamond based on either the absence of color (white diamonds) or the hue, depth, and purity (colored diamonds).
Conflict Free Diamonds: diamonds that come from regions not known for warfare. Vintage diamonds that were mined and cut prior to the development of civil conflicts.
Crazing: refers to the tendency of Opals to crack when exposed to heat or dry air.
Crown: lies above the girdle and is the upper portion of a diamond’s cut.
Crown angle: number of degrees between the table and the bezel facets.
Crystal / Mineral Inclusions: some diamonds will have small crystals, minerals, or other diamonds as inclusions. Some are small and invisible to the naked eye, some are more prevalent. While some Crystal / Mineral Inclusions can add to the look of a diamond, others can affect the overall clarity grade.
Culet: located at the bottom of the stone and is the smallest facet of a diamond.
Cut: determines the brilliance of a diamond. Jewelers and gemologists use cut grade as a way to determine diamond’s proportions, quality of polish, and light reflectivity.
Depth: distance between cutlet and table. Usually measured in millimeters.
Depth Percentage: Measures the ratio of depth to the total diameter of a diamond.
Deep Cut: known for poor light reflectivity. This cut makes the stone appear dull.
Diamond Cutting: A process by which raw diamonds are cut and polished to maximize their brilliance.
Diamond Gauge: a tool used to measure dimensions of a diamond.
Diamond Plot: a document used by the GIA to map diamond’s inclusions and blemishes.
Dispersion: reflected light also known as fire. Dispersions occurs when white light is separated into multiple colors.
Dossier: abbreviated GIA grading report used for smaller diamonds.
Emerald Cut: A square or rectangular cut. This cut is widely used in cutting emeralds to maximize the natural beauty of the stone.
Enhancements: specific treatments that are applied to a polished and cut diamond to maximize its brilliance and enhance the stones appearance. Enhancements can include treatments like: sealant application to fill any cracks that may be present in the stone, laser drilling to remove inclusions, treatments to improve color or treatments to add color.
Eye-Clean: a term used to describe a stone where inclusions / blemishes are not visible to the naked eye.
Excellent Make: reface to a high quality polish and symmetry.
Extra Facet: a facet that is not part of the original cut. Usually created by the craftsman due to the flaw or imperfection in the stone.
Etch Channel: irregular shapes or tunnel like structures that are etched into the diamond’s crystalline structure during the process of formation.
Facet: smooth flat surface of a diamond. Facets allow light to enter and reflect at multiple angels giving the stone its brilliance.
Fancy Shape: all diamond shapes / cuts other than round.
Feathers: cracks or striations inside the diamond that resemble feathers. Usually feathers do not impact the durability of a diamond unless they run through the entire length of a stone or are located close to the surface in which case there is a possibility that the diamond will break with age.
Finish: refers to the qualities imparted to a diamond through the process of cutting and polishing.
Fluorescence: a soft colored glow that is emitted by a diamond when the stone is exposed to a UV light.
Foil Backed: addition of foil to the back of a gemstone to improve its color or brilliance.
Gemological Institute of America (GIA): one of the most unbiased and respected gem grading labs in the world.
Geode: a formation that contains quartz or other gemstone crystal inside a hallow cavity.
Girdle: The outer edge of a diamonds shape. The area where the crown and the pavilion meet.
Grain Lines: crystal inclusions in a diamond that are shaped like a line.
Good Make: one of more economical brilliance grades. A good make will reflect most of the light that enters the diamond.
Hardness: diamond is the hardest known natural mineral on the Mohs scale. The hardest diamond has been measured at 7.5-10 on the Mohs scale. The hardness of a diamond is largely dependent on the amount flaws present in the stone as well as its crystalline structure. The hardest diamonds originate from the Copeton and Bingara area in Australia and are usually used for industrial polishing and cutting.
Heart-shape Cut: a diamond cut that take a form of a heart. This shape is popular in engagement rings and pendants.
Ideal Make: preferred brilliance grade.
Inclusion: internal flaws. Usually characterized by the presence of carbons, crystal or mineral formations, or cracks inside the stone.
Intergrowth: two or more inclusions that have intertwined together during the formation process.
Kimberly Process: is a process that was developed to monitor worldwide trade of rough diamonds. During this process, each country certifies their diamonds before exporting them. This process does not apply to the internal diamond trade.
Knots: effect clarity and durability of a diamond. Knots are diamond crystals that extend to the surface of the diamond.
Laser-Drill Holes: man made inclusion designed to raise / enhance the clarity grade of some diamonds.
Length-to-Width Ratio: used to analyze the outline of fancy shaped diamonds.
Marquise Cut: elongated cut that resembles a football.
Measurements: diamond’s length, width, height, and symmetry are measured in millimeters and are used to identify the quality of its cut.
Naturals: small parts of the original, rough diamond that are left near or around the girdle.
Oval Cut: elongated version of a round cut.
Pave: multitude of small diamonds set close together to create and illusion of large diamond or to enhance the brilliance of a center diamond.
Pavilion: located at the bottom of the diamond. The pavilion is crucial to the reflectivity of a diamond.
Pear Cut: teardrop shaped diamond
Pinpoint Inclusions: as the name implies, these are small, usually white inclusions.
Point: a unit of measurement. 1 point is equal to one-hundredth of a carat.
Polish: blemishes that are not severe enough to effect the clarity grade of a diamond.
Princess Cut: square or rectangular shape. Very popular in engagement rings.
Proportions: the number of facets and their size, an integral part of determining the quality of a diamond’s cut.
Radiant Cut: resembles a square or a rectangle with rounded corners.
Ratio: comparison of length versus width of a diamond
Semi-mount: a setting popular in engagement rings where the side stones are already set with the center piece stone being chosen by the customer.
Shallow Cut: creates an illusion of a larger stone. However, light can escape the shallow cut through the sides instead of reflecting off of the top of a diamond. Shallow cut diamonds are not as brilliant as ideal cut.
Single-Cut: a diamond with 15-17 facets.
Step Cut: square or rectangular cut diamonds. The facets in this cut run parallel to the girdle.
Symmetry: quality indicator of a diamond’s cut.
Surface Property: diamonds are naturally lipophilic and hydrophobic which means that diamonds surface can’t be easily wet by water but can be easily stuck by oil.
Table: the largest facet of a gemstone.
Table Percentage: a ratio between of width between the top facet to the width of the entire gemstone.
Trilliant Cut: triangular cut.
Yield: weight of finished stone that are cut from the rough.
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