Jewelry Design & Manufacture | Gemological Terms
Below we have listed terms that might prove to be useful to you. These are typical gemological terms used in custom designed, handcrafted gold, platinum and silver jewelry including diamond engagement rings, wedding bands, commitment rings, unique earrings and pendants, and stunning bracelets.
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Rectangular gem: a gem cut into a long rectangular shape.
A traditional step-cut crown and a modified brilliant-cut pavilion. A square barion cut gem has 61 facets, excluding the culet.
Bearding or girdle fringes
Also called bruiting. The outermost edge of a gem, called the girdle, can develop small cracks that resemble whiskers during the polishing process. The bearding can sometimes be removed, if not too dramatic, with slight re-polishing, and if the weight allows.
The term blemish is used when a gem has scratches or marks on the external area of the stone.
Liveliness, or sparkle in a stone when light is reflected from the surface and from the total internal reflection of light.
Brilliant cuts are often considered to have the most brilliance of all cuts. Distinguished by pavilion facets that are perpendicular to the girdle of the gem.
A facet-less style of cutting that produces a smooth rounded gem. They can be in many shapes, including round with high domes to squares.
A unit of weight utilized in gemology. . 1/5th of a gram. One carat can also be divided into 100 “points” which refers to percentage points. Thus a .50 carat gem is sometimes referred to as a 50 point gem or a ½ carat gem.
Certification (or Diamond Grading Reports)
There are many recognized gemological laboratories that can grade your stones for a fee.
Most gems have natural imperfections, commonly referred to as inclusions, which contribute to its identifying characteristics. Inclusions are found within the gem, and tend to interfere with the passage or reflection of light by the gem. Most are undetectable by the human eye, and can only be seen with 10X magnification. Inclusions are ranked on a scale called clarity; the fewer inclusions, the higher the clarity.
A natural area of the gem, especially a diamond, where a weak bond holds the atoms together. The gem will be split along these planes by the cutter.
This setting surrounds a larger center stone with several smaller stones. It is designed to create a beautiful larger ring from many smaller stones.
All gems are graded on a color scale established by the Gemological Institute of America (GIA).
Group of gems with graduated color.
The portion of a gemstone above the girdle.
The bottom point of a gem. It may be polished in some stones. Sometimes, a cutter may choose to make the culet a surface instead of a point.
A mixed-cut gem shaped like a square pillow.
Cut refers to the angles and proportions of a fashioned gemstone. Based on scientific formulas, a well-cut gemstone will internally reflect light from one mirror-like facet to another and, disperse and reflect it through the top of the stone. This results in a display of brilliance and fire. Gems that are cut too deep or too shallow lose or leak light through the side or bottom, resulting in less brilliance, and ultimately value.
Styles are different than shapes. The simplest and most common way to explain cutting style is to categorize it into the following three basic types: Step-cut, Brilliant-cut and Mixed-cut.
A diamond is the hardest known natural substance. It is crystallized carbon. Diamonds are mined in their rough form and then, cut and polished to reveal their brilliance.
Distribution of white light into its various colors is known as dispersion, or the display of the spectral colors.
A rectangular or square-shaped cut-cornered gem. A form of step cutting, this cut is favored for its ability to enhance color rather than brilliancy. It is also sometimes used to emphasize the absence of color in diamonds.
Any process used to make a gem more visually appealing or more durable. Fashioning a gem by cutting is called a natural enhancement. Generally, given similar materials, the less enhanced a gem, the more valuable.
Any flat polished surface of a gemstone.
A cut other than round -- such as baguette, emerald, pear, marquise, square, oval, heart, etc.
A process that injects a substance into a gem to hide inclusions. A form of “enhancement”. Feather -- A type of inclusion or flaw within a gemstone. It is described often as a small crack or fissure.
Describes the exterior of a gemstone. If a gem is well polished, it has a very good finish.
Often a term used instead of "dispersion," it is the variety and intensity of rainbow colors seen when light is reflected from a gemstone.
When exposed to ultraviolet light, a gem may exhibit a more whitish, yellowish or bluish tint, which is called fluorescence. The untrained eye can rarely see the effects of fluorescence. Gem reports often state whether a gemstone has fluorescent properties. Fluorescence is not considered a grading factor, only a characteristic of that particular gem.
The outer edge of a cut stone, the dividing line between the crown and the pavilion. Sometimes the girdle is polished and sometimes it is unpolished. Ideally the width of the girdle should be even and proportional to the cut of the stone.
Growth or grain lines
These can be considered internal characteristics, and can often be seen only by rotating the gem very slowly. They can appear and disappear almost instantaneously. They appear as small lines or planes within the gem.
Resistance a material offers to scratching or abrasion. Generally measured using the MOHS scale.
"Internal characteristics" apparent to a trained or professional eye at 10x magnification. Inclusions can be bubbles, crystals, carbon spots, feathers, clouds, pinpoints, or other impurities, or even cracks and abrasions. They are what make a gem unique, as a fingerprint does for a person.
A setting that is designed to make a gem appear larger.
Any small magnifying glass mounted for hand use, to hold up to the eye socket or attach to a pair of glasses.
The hue and depth of reflection from pearls, opals or other opaque stones.
A double-pointed, boat-shaped stone that is long and thin with gently curved sides coming to a point on either end. Marquise is part of the brilliant-cut family.
This cut has both step-cut and brilliant-cut facets.
A scale of hardness with numbers from one to ten assigned to ten minerals of increasing hardness from talc to diamonds.
Mellee or Mele
Small gems, usually less than 1/10th carat. Rhymes with jelly.
A characteristic that is part of the surface of a polished gemstone. It is a small feature of rough crystal surface that was left during the cutting process normally occurring on or very near the girdle of some gems.
This technique is commonly used on emeralds. The purpose of this technique is for the oil to fill the fine cracks that weaken the green color. The oil fills the cracks making them "disappear" and thereby improving the color.
The portion of a gemstone below the girdle.
Term used to describe any gem whose girdle outline resembles a pear shape.
A small inclusion within a gem. A gathering of pinpoints is called a "cluster" or "cloud." A cloud or cluster can appear as a hazy area in a gem, a pinpoint appears as a dot.
Term meaning one-hundredth of a carat; a percentage point.
The finish applied to the surface of a gem.
A square or sometimes rectangular-shaped modified brilliant-cut gem. Proportion the relationship between the angles of the facets of the crown and pavilion.
A rectangular or square shaped gemstone with step-cut and scissor-cut on the crown, and a brilliant-cut on the pavilion.
The bending of light rays as they pass through a gemstone.
Light reflected directly from the surface of a gem.
Rows of facets that resemble the steps of a staircase, parallel to the girdle of a gem. The emerald cut and the baguette are examples of the step cut.
The top surface of a faceted gemstone.
This is typically the largest facet on a gem. It is located on the top of the gem. The table facet is sometimes referred to as the "face."
Term used to describe the diameter of the table facet in relation to the girdle diameter of a gemstone.
A triangular-shaped gem with slightly curved sides.