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Gemspedia >> Gems >> Gems Manufacturing Process

Gems Manufacturing Process

Cutting (also know as lapidary) is the process whereby a rough stone is turned into a gemstone. The process makes a gem assume a certain shape, bringing out its luster and color, enabling it to be set into jewelry.


Unlike diamonds, colored gems possess variable optical properties and are not cut to a uniform ideal. A well-cut colored gem exhibits even color, an acceptable number of inclusions, good brilliance and shows the majority of carat weight when viewed from the top.

 

Broadly, the styles of gem cutting can be divided into faceted gems (those with geometrically shaped flat polished faces) and non-faceted gems (those that do not have geometrically shaped flat polished faces such as cabochons). The steps in faceting gemstones are:

 

Slicing: Also called sawing, slicing is one of the most crucial stages in the finishing of gemstones (if not the most crucial), as it will ultimately determine the size and beauty of the finished gem. Once the rough is selected, using a diamond-tipped circular steel saw, the gem slicer will determine how to cut, where to cut, and how many pieces to cut, in order to produce the highest quality. If the rough is cut incorrectly its beauty may be diminished, relegating an exceptional gem to the ordinary.

 

Pre-forming: Once the rough has been carefully sawn, pre-forming commences. This process requires tremendous experience and concentration. Pre-formers carry a great responsibility, as they determine both shape and orientation for each gemstone; mistakes at this stage can be catastrophic. Apart from beauty, pre-formers always bear in mind the weight of the finished gem. Pre-forming is typically performed by using a vertical steel grinding wheel.


Shaping: The shaper uses a special type of heat activated resin to affix the pre-formed gemstone onto a metal rod, commonly called a dop stick. The shaper then delicately applies the gemstone to the shaping wheel to obtain a more accurate presentation of the facets and size. Due to the immense precision required by this process, the shaper is usually a very experienced pre-former. Shaping is completed using a hand-operated shaping wheel.


Polishing: The final step is known as polishing. Once gemstones have reached their ideal size and shape, they are taken to a steel (or steel and copper) horizontal polishing wheel where the polisher completes the faceting and gives them a final polish using fine diamond paste to reveal their hidden luster, brilliance and fire.

 

With a few months training, gem cutters can facet 20–30 gems per day. But it may take many years to become a skilled preformer.

 

The cut of a gem is a combination of its shape and faceting style. Shape largely depends on the original shape of the gem rough (i.e., the shape of the raw gem crystal as it comes from the earth). The oval shape is most frequently used, as it best balances beauty and carat weight retention. Factors to consider when choosing to facet a gem in another shape include design aesthetics, inclusions, carat weight loss and color.

Common gem shapes

Brilliant cut

The brilliant cut is the standard for diamond, but also used on other gems. It typically has 57 facets, or 58 with a culet. Although no single person has officially been credited with its invention, a Venetian cutter named Vincenzio Perruzzi is often mentioned, with its introduction occuring in the 18th century.

The brilliant cut

The modern brilliant cut is the result of the work of a number of individuals in the late 19th and early 20th centuries, most prominently Henry Morse and Marcel Tolkowsky. Through both practical experiments and theoretical suppositions, the proportions necessary to create the best balance of brilliance, dispersion and scintillation (play of light) were calculated. While these “ideal proportions” are important in the diamond trade, they are much less so with colored gems, even when cut in the brilliant style. This is because colored stone lapidaries must pay greatest attention to color, as opposed to maximizing factors like brilliance or dispersion.

 

The brilliant cutting style is extremely flexible and today it is applied to a variety of shapes other than round. These include pear, marquise, cushion, and heart shapes

Step (emerald) cut

Next to the brilliant, the other major facet style used is the step cut, also termed the trap or emerald cut. It is used on stones of rectangular, square or angular outline, with corners truncated slightly to prevent chipping or fracture. The step cut’s long, unbroken facets display the gem’s color to maximum advantage. However, since inclusions are more noticeable, this cutting style works best with relatively clean or richly- colored material.

The step or emerald cut

The step cut was developed specifically for emeralds to reduce the amount of pressure exerted during cutting and to protect the gemstone from chipping. Today, modern cutting techniques make this less important and it is used for a wide variety of gem types.

 

Mixed cut

The cutting style most often used for rubies, sapphires and other colored gems is the mixed cut, so-called because it combines a brilliant cut crown with a step cut pavilion. Its chief advantage lies in the fact that the cutter can retain as much weight as possible by rounding off the steps, or facet rows, on the pavilion. This extra weight retention, however, does not come without a price. If the facet rows nearest the girdle are cut too steep, extinction is created, with light passing out the side instead of returning to the eyes as brilliance.

The mixed cut

Barion cut

Developed by South African diamond cutter Basil Watermeyer in 1971, barion cuts allow adaptation of the round brilliant style of pavilion facets to angular shapes, such as the emerald, square emerald, kite, triangle, pentagon and hexagon. Their key features are half-moon shaped pavilion facets at the girdle, which allow brilliant-style facets to be placed upon angular-shaped stones. The crown is cut in the standard step-cut style. Barion cuts produce as much or more brilliance than even the standard round brilliant cut, as well as greater weight retention. Unlike step cuts, barions do not allow rounding of the pavilion (which gives greater freedom in weight retention).

The barion cut

Princess cut

A more recent adaptation of the barion is the princess cut, which often finds its way into solitaire engagement rings. Flattering to a hand with long fingers, it is often embellished with triangular gems at its sides. Because of its design, this cut requires more weight to be directed toward the gem’s depth in order to maximize brilliance. The advantages of the princess cut are not restricted purely to diamonds; it is also used on many other gems. Because of the extra faceting, and the effects this produces, princess cuts are naturally more brilliant and sparkly.

The princess cut

The princess cut generally works best with lighter colored transparent gemstones and along with the antique cushion cut, the princess cut maximizes a gem’s luster. It was designed for weight retention of octahedral diamond crystals, helping to create more attractive diamonds at more reasonable prices.

 

It is a relatively new cut and often finds its way into solitaire engagement rings. Flattering to a hand with long fingers, it is often embellished with triangular gems at its sides. Because of its design, this cut requires more weight to be directed toward the gem’s depth in order to maximize brilliance. The advantages of the princess cut are not restricted purely to diamonds; it is also used on many other gemstones. Because of the extra faceting, and the effects this produces, princess cuts are naturally more brilliant and sparkly.

 

Trilliant (trillion) cut

The standard number of facets of a trilliant cut gemstone is 43. Trilliant cut gemstones are based on a triangular shape. Usually with truncated corners and displaying a variety of facet designs, this cut creates a spectacular wedge of brilliant fire. The tips and culets of trilliants are pointed and thin. As a result, some jewelers only bezel-set trilliants, even though prongs that protect the tips work well and show more of the gem.

The trilliant cut

As you look down through the gem, the culet generally appears centered in the middle of the table showing the pavilion of the gem with an attention to symmetry. When you examine the gem in profile, the girdle and table facet are generally parallel. The pavilion’s main facet usually extends from the culet perpendicularly until it intersects the girdle. Because of their equilateral form, trilliants return lots of light and color. They are considered nearly as brilliant as round cuts, so they are a great choice for customers who like brilliance, but want something other than round. Variations include rounded-corner triangles, modified shield cuts and triangular step cuts.

 

There should be as few polishing marks as possible and the surface should appear glossy and reflective. Good polishing helps maximize brilliance and scintillation in trilliants.

 

Trilliants work well with light-colored gems, such as diamonds, aquamarines, beryls and white sapphires, where cutters try to maximize brilliance. Inversely, some cutters use trilliants to effectively lighten and brighten the appearance of darker gems such as tanzanite, spessartine garnet, rhodolite garnet and amethyst.

 

First developed in Amsterdam, the exact design can vary depending on a particular gem’s natural characteristics and the cutter’s personal preferences. It may be a traditional triangular shape with pointed corners or a more rounded triangular shape with 25 facets on the crown, 19 facets on the pavilion and a polished girdle. Some twinned diamond rough (a type of crystal intergrowth) is naturally triangular (these are called macles) and is ideal for trilliants.

 

Briolette cut

The briolette is believed to derive its name from the French words brilliant (sparkling) and brignolette (a small dried plum). It consists of a drop or pear-shaped gemstone with shaped facets all the way around. There is no table, crown or pavilion.

 

Considering the shape of the briolette, it is the most difficult to cut and an experienced cutter can only produce 5–10 briolettes per day. While the approximate number of facets of a briolette is 84, the more facets the drop has, the more brilliant it is. Because of the specific number of facets, the briolette requires perfection from top to bottom.

The briolette cut

The briolette is a type of rose cut, which dates back to the 14th century or earlier. No one knows for certain how old the briolette cut actually is. There are rumors of diamonds cut in India during the 12th century exhibiting this style of cutting. The briolette is a relatively rare diamond cut and far more common for colored gemstones. Most diamond briolettes are cut from white rough, but colored diamond briolettes, especially fancy and canary yellows, are becoming more popular.

 

Briolette gems are found in antique tiaras and estate jewelry from the Victorian, Edwardian and Art Deco eras. Today, briolette gems are increasingly popular in fashion jewelry. Briolette cuts are primarily set in earrings, necklaces and pendants. They are often used for earrings with a hanging wire or a simple precious metal cap, sometimes with a small diamond accent. Briolettes have been featured in many industry publications and also in Vogue and Harper’s Bazaar. Every briolette is unique, so look for beauty and lots of brilliance. 

 

Cabochon cut

The word cabochon is derived from the old Norman French word caboche, meaning head. A cabochon is a polished gemstone with a flat bottom (or slightly rounded bottom) and a convex or rounded domed top. The traditional cabochon is an oval but cabochons can also be fashioned into other shapes including triangles and rectangles.

 

Cabochons, commonly known as cabs, are the oldest and most common form of gem cutting. Gems cut en cabochon are shaped and polished, rather than cut. In antiquity, this was generally the only cutting option available other than using the gem with the natural facets of their crystal structure. Some of the most beautiful ancient jewelry was made with cabochons, including that of India and the breastplate of Aaron.

The cabochon cut

Cabochons are used for making jewelry, often carved as intaglio (a gem carved in negative relief) or cameo (a gem carved in positive relief), and are also used in crystal healing. Today, the cabochon cut is applied to gems of limited transparency (e.g., turquoise, jade, agate, etc.) or as a result of predominant inclusions (e.g., relatively opaque sapphires, rubies or emeralds) or for gems where the cut’s curved surface accentuates special characteristics (e.g., iridescence, chatoyancy or the cat’s eye effect, asterism or the star effect, etc.).

 

Buff top cut

A cabochon variant for transparent gems, the buff top cut mixes a faceted cut with a non-faceted cut. This results in a gem with the typical domed top of a cabochon and a faceted pavilion, giving the illusion of depth as the eye is drawn into the center of the gem. The cut shows good brilliance and has a crown that is less easily abraded than those of faceted gems.

 

Concave cut

The concave cut is a three dimensional conical shaped facet applied to the pavilion of the gem that creates depth as well as length and breadth. Instead of the facets being joined by an angle they are joined with a groove. This third dimension allows the gem to refract more light, thereby maximizing its brilliance. The concave cut also distributes light more evenly, giving the gem a homogeneous interior glow.

 

While it is sometimes confused with the millennium cut it can be easily distinguished by the lack of a standard number of facets and its application only to the pavilion.

 

While Doug Hoffman patented concave cut technology in the early nineties, his friend Richard Homer is credited as perfecting the technique of the concave cut. While working towards a Geology Degree, Homer began cutting gems in 1974 to help pay his tuition. Since then, his designs have won 15 American Gem Trade Association (AGTA) Cutting Edge Awards.

 

Not all gems benefit from the concave cut. Optimizing color and light is always the first consideration in cutting, and although diamonds and lighter-toned gems increase up to 100% in brilliance when concave cut, darker gems like rubies can appear murkier and less attractive. Furthermore, the concave cut is more expensive than traditionally cut gems, due to the higher weight loss and the additional labor required.

 

Mirror cut

The mirror cut is characterized by an extraordinarily large table and thick girdle consisting of as much as 90% of the width of the gem. This makes the gem highly refractive and literally gives it the properties of a mirror, hence the name.

 

Sometimes referred to as the thin stone, the mirror cut was an early 16th century phenomenon that is making a comeback. It is a variety of the round cut and appears in the names of some historic diamonds including the “Mirror of Portugal” and the “Mirror of France.”

 

Fancy cut

For those who want something really different, recent advances in cutting technology have produced a breathtaking range of innovative new shapes such as flowers, clover leaves, stars, triangles, kites and all manner of fancy cuts.

 

Some of the new designs are variations on standard shapes, aimed at creating the illusion of a bigger, more perfect gemstone. Others play with the natural rough and still others are fashioned into revolutionary new shapes.


The important fact to remember is that this ever-widening choice of shapes and designs is being created to suit a variety of individual styles and tastes. No one cut is more beautiful than another. The magic of nature and the artistry of the cutter combine to make each a unique work of art.


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