How To Talk About Gemstones and Jewelry
There is much to know that pertains to the specifics of how jewelers and gemologists will speak about jewelry and gemstones. The more knowledgeable you make yourself, the better you will be prepared to know exactly what is being discussed and what that means for the gem or piece of jewelry you are considering. We have compiled the most helpful information on this page so that every purchase can be one of extreme confidence.
Faceted Gemstone Terminology
In antiquity, if emeralds were worked at all, they were fashioned into cabochons. Cabochons are the simplest cutting style. They have a curved upper surface and a flat or curved underbelly. The upper portion of a cabochon may be a simple dome or a series of curved surfaces that meet in a pyramidal arrangement (e.g., a sugarloaf cabochon). A cabochon may be any shape, but circles and ovals appear most often.
It costs less to create a cabochon than a faceted stone, and the quality of the rough is less critical. Cabochons can be made from lower quality material that is considered unsuitable for faceting. Today, trapiche emeralds and cat’s eye emeralds are cut into cabochons to display their special phenomena.
The advent of improved gem cutting technologies enabled lapidaries to cut facets into gemstones. Facets are the flat, polished surfaces of a finished gemstone. In the early days of gem cutting, many stones were table cut, which created a single polished face on the top of the stone.
Later, rose cuts became popular. A rose cut stone typically has a flat bottom and radiating triangular facets that come to a point at the top of the stone. Today, we use three key cutting styles to create faceted stones: brilliant cuts, step cuts, and mixed cuts.
The girdle is the narrow edge around the part of the stone with the widest diameter. It separates the gemstone’s crown and pavilion. The tiny facet at the very bottom of the stone is called a culet. Culets can very in size, but they are usually very small. Sometimes the point of the stone is called a culet even if the stonecutter created no additional facet. Other brilliant cuts such as hearts and pear cuts have a few more components.
While brilliant cuts employ radiating facets, step cuts consist of parallel facets. A majority of emeralds are cut in a variation of the rectangular step cut, often known as an “emerald cut.”
While the facets of a brilliant cut create a lively play of color, the geometry is a poor match for most emeralds because it creates a large amount of wasted rough. The parallel arrangement of step-cut facets allows cutters to adjust the finished stone’s proportions to the shape of the rough crystal. Step cut emeralds may not sparkle like those with brilliant cuts, but in exchange they offer broad, uninterrupted expanses of color.
The mixed cut combines a brilliant cut crown with a step cut pavilion. Mixed cuts offer significant advantages over brilliant cuts and step cuts. The crown of mixed cuts is brilliant cut to maximize the brilliance and sparkle of the stone and to obscure minor clarity issues. The pavilion is step cut to save weight and bring out the color of the stone.
Briolettes are stones cut in the round to make a faceted teardrop shape that looks especially appealing when dangling from an earring or pendant.
Additional information for evaluating cut is provided in the discussion of Tips for Buying Emerald Jewelry.
Brilliance describes the amount of light that a cut emerald reflects back to the viewer from the interior of the stone. Brilliance is a consequence of cut, and it is an important characteristic because it determines the perceived liveliness and color of a gemstone.
To understand brilliance, we need to follow the path light takes as it travels through a faceted gemstone. White light entering an emerald from above travels through the gem in a straight line. As it does so, some of the component colors of the visible spectrum are absorbed. The spectral colors that are not absorbed determine the stone’s color. For example, an emerald will absorb most of the red, and some of the blue and yellow portions of the visible spectrum, leaving mostly green to be reflected back to the eye of the viewer.
When light passing through the crown reaches the rear or pavilion facets of the emerald, it can either travel right out through the bottom of the emerald or reflect back into the stone, depending upon the angle at which it strikes the facet.
If light passes straight through the stone, it won’t return any brilliance to the viewer. Light that reflects off of the pavilion facets and then exits the stone through another part of the pavilion doesn’t return any brilliance to the viewer either. Only those light rays that reflect back out through the crown toward the eye of the viewer provide brightness and color. These rays account for an emerald’s brilliance.
To evaluate brilliance in a cut emerald, hold the stone level under overhead light and look directly down at the crown. You’ll probably notice some very pale or weakly colored areas. If so, you are looking through what jewelers and gemologists call a window in the stone. A window is an area where light passes right through a cut stone without reflecting back at all. Even the most carefully cut emerald will show windows at certain angles, but windowing should be minimal, or completely absent when a stone is viewed from directly above.
You may also see that some parts of the stone look very dark – maybe even black. These dark areas are called extinction areas, and they occur where light leaches out of the sides of the pavilion, rather than returning to the viewer.
It is important to understand the basics of gemstone mountings and settings. A mount refers to the entire precious metal object before stones are set into it. Mounts include rings, necklaces, pendants, earrings, bracelets, brooches and cufflinks. Gemstones are incorporated into mounts with a variety of popular setting styles including the following:
Bezel setting: a setting where a strip of metal encircles the edge of the stone. It is also called a rub-over setting. This is a popular means of setting cabochons.
Prong setting: a popular setting style (also called a claw setting) wherein pointed, rounded, flat, or v-shaped metal supports called prongs or claws are used to hold a stone. A combination of four or six prongs is the norm, but more may be used depending on the style and desired effect.
Flush setting: this kind of setting does not have prongs or a bezel. Gems are set directly into the jewelry so that the top of the gem is flush with the metal surrounding it.
Pavé setting: a popular setting style where the stones are placed close together to hide the metal mount. The name comes from the fact that the finished piece looks like it is paved with stones.
Channel setting: a setting where stones are set into a grooved channel with no metal separating them. A bar setting is similar, but stones is held in place by parallel bars on either side.
Invisible setting: a difficult setting to execute, stones are grooved just below their girdle and slid over wire supports. This allows many gems to be placed together with no gaps between them. This setting was invented by the famous design house Van Cleef and Arpels.
Tension setting: a modern setting that requires no bezel or prongs where the stone seems to float in mid-air. In this setting, a gemstone is held in place by the precious metal shank or band, which presses on the stone’s girdle in a spring-like manner.
Precious metals are made into jewelry by employing four common methods: die striking, wax casting, electroforming, and hand fabrication. These techniques are not mutually exclusive; finished jewelry is often a composite or combination of pieces created via these different manufacturing methods.
Die striking or stamping is a very old technique for creating jewelry. It can be a rapid and cost effective means for producing large quantities of goods. Another benefit of the die striking or stamping process is the fact that it produces dense and durable goods that wear well and take a high polish. Because it produces items that are naturally strong, the die striking process is especially recommended for the manufacture of prong settings, although it is also commonly used to make pendants and earrings. The process begins with the creation of a die, which is usually comprised of two parts–a punch and a mold. The dies are mounted into powerful machines that are fed blanks of precious metal. When the blanks are struck by the die, a three dimensional piece of jewelry is created.
Modern wax casting methods are derived from an ancient Egyptian technique. Although the results are not as dense as die struck pieces, the casting technique is a relatively rapid and economical means of making many identical jewelry pieces. Today, the process involves making a wax model in a rubber mold. Identical wax models are then attached to a wax “tree” and covered with a plaster-like material, called investment. Once the investment has dried, it is heated and melted wax is drained from the mold. The hollow space left behind is then filled with molten metal, which is allowed to solidify. When the investment is removed, the result is a precious metal “tree” of castings. The castings are clipped from the trees, cleaned, and polished.
Electroforming is a technique that uses electricity to deposit metal over a model. Electroformed jewelry is not as durable and more difficult to repair than jewelry produced by other means, but the products are lightweight and often intricately detailed. In this technique, a wax model is attached to a frame and submerged in a special chemical bath. An electrical current gives the models a positive charge, which attracts negatively charged particles of precious metal. When the metal layer is thick enough, the wax model is melted away, and a hollow piece of precious metal jewelry is created.
In an age dominated by mass production, it is uncommon to find one-of-a-kind hand fabricated jewelry pieces. When a jewelry item is hand fabricated, it means that it is made entirely with hand tools and methods including sawing, carving, hammering, soldering, setting, and finishing. These techniques are time consuming and require great skill. Because there is some ambiguity in the term “hand made,” jewelers generally prefer to use the more precise term “hand fabricated.”
Using A Loupe
A 10x lens or loupe is one of the most valued of all instruments for gemological observation and identification. Not only is the loupe easily transportable and inexpensive; it is useful for identifying items of any size, transparency, or condition. It is invaluable for examining both the surface features and interior of both fashioned gemstones and rough material.
When using the loupe, the primary goal is to position and maintain the eye, the lens, and the object at a fixed distance from one another. This is done by first resting the hand holding the loupe on the cheek and then positioning the loupe about one inch from your eye. The gemstone or object being examined should be held in the other hand (often in tweezers or a stone holder). To steady yourself, keep both hands in contact with each other as the object is viewed. You may also lean onto a table or lock your elbows to steady yourself.
Keep both eyes open when viewing an object. If you wear glasses, they may be left on while using a loupe. Remember to relax and breathe normally. Turn the stone to view it from different angles without losing focus—keeping the distance from the eye, the lens, and the objects fixed.
Lighting is important. Stones should be lit from the side or the back and examined against a non-reflective background. You should avoid direct sunlight when using a loupe, but daylight is good for examining stones. Table lamps and penlights are also recommended as illumination sources. If you use a table lamp or penlight, hold the stone under the light, but keep the loupe itself out of the light.
Now that we’ve covered this additional terminology, we next explore our Glossary for more description of words and concepts.