Gems TV

GEMSTONE CUTTING

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 lustre and colour, enabling it to be set into jewellery.

Unlike Diamonds, coloured gems possess variable optical properties and are not cut to a uniform ideal. A well-cut coloured gem exhibits even colour, 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 (gems with geometrically shaped flat polished faces) and non-faceted gems (those gems that do not have geometrically shaped flat polished faces such as cabochons). The steps in faceting gemstones are:

The cut of a gemstone largely depends on the shape of the gem rough (i.e. the shape of the raw gem crystal as it comes from the earth). The Oval cut 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 colour. Gem cutters are considered “experts” once they have 2 years of experience and on average can facet 30 gems per day.

Round brilliant cut

Round is from the Middle English word “rounden”, which means “secret”. The Round Brilliant cut is also known as the Round cut, American Ideal cut or American Standard cut.

The standard number of facets of a Round Brilliant cut gemstone is 57. Although no single inventor has officially been credited with the invention of the Round Brilliant cut, many sources do credit a Venetian cutter named Vincenzio Perruzzi and date the Brilliant’s introduction to the 18th century.

The Russian mathematical genius Marcel Tolkowsky, a member of a large and powerful Diamond family, subsequently calculated the cuts necessary to create the ideal Diamond shape. As part of his PhD thesis in mathematics, Tolkowsky considered variables such as the index of refraction and covalent bond angles to describe what has become known as the Round Brilliant cut. Tolkowsky’s recommended cut height for a Round Brilliant is 57.6% that of the diameter of the Diamond, which breaks down to about 43% for the pavilion, and 16% for the height of the crown. This 57.6% is probably the most crucial dimension of the gem. This cut is optically the most efficient. The Round Brilliant boasts one of the best recoveries for well shaped Diamond and gemstone rough; this translates into good value for consumers.

The Round Brilliant cut is designed to provide maximum optics for brilliance and scintillation (play of light), making the gem sparkle and dance in the light. This cut was specially developed for Diamonds but is today common for all gem types.

Oval cut

Oval is from the Latin word “ovum” meaning “egg”. The standard number of facets of an Oval cut gemstone is 69 and it has an elliptical shape when viewed from the top.

For the Oval cut, the ratio of the length to the width should be approximately 2:1, although this does vary slightly depending on the optical properties of different gem types. A well cut Oval gemstone can be nearly as bright as a Round Brilliant cut.

The Oval cut is a particularly beautiful shape and if well proportioned gives great scintillation and fire.

Baguette cut

While Baguette is from the Italian word “bacchetta”, meaning “rod or stick”, to the Native American Navajo, the oblong symbolises the female form, intelligence and divine contemplation.

The Baguette shaped gemstone is really only a special oblong shape and has approximately 20 facets. Most oblong cuts are “step” cut, which means that the facets on the pavilion have been cut in steps, parallel to the edges, in the manner of a pyramid with its top chopped off. The base and table are square with triangular facets.

The Baguette cut best suits gem types whose rough crystals occur in a similar shape (e.g. Tourmaline).

Square cut

Square is from the Vulgar Latin word “exquadra”, meaning “square shape”.

The standard number of facets of a Square cut gemstone is 57 and is really only a special oblong shape where the sides are the same length. Most oblong cuts are “step” cut, which means that the facets on the pavilion have been cut in steps, parallel to the edges, in the manner of a pyramid with its top chopped off.

Some believe this cut is a symbol for equality, fair mindedness, justice, order, satisfaction and truth.

Trilliant 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 jewellers only bezel-set Trilliants, even though prongs that protect the tips work well and show more of the gem.

As you look down through the gem, the culet generally appears centred 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 colour. 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 maximise brilliance and scintillation in Trilliants.

Trilliants work well with light-coloured gems - such as Diamonds, Aquamarines, Beryls and White Sapphires – where cutters try to maximise brilliance. Inversely, some cutters use Trilliants to effectively lighten and brighten the appearance of darker gems such as Tanzanite, Spessartite 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 crystal growing within a crystal) is naturally triangular (called “Macle”) and is ideal for Trilliants.

Pear cut

The standard number of facets of a Pear cut gemstone is 71. A hybrid cut, combining the best of the Oval and the Marquise, it is shaped like a sparkling teardrop. A nice Pear cut is generally one that is well cut with a polished girdle.

Although it varies depending on the optical properties of each gem type, Pear cuts should generally have a good depth such as 1.5:1 aspect ratio for a great look and a lively gem. For rings, this cut compliments a hand with small or average length fingers. It is particularly beautiful for pendants and earrings.

While colour shows fairly dramatically in a Pear cut gemstone, the world’s largest cut Diamond (the Cullinan I mounted in the British Royal Sceptre) is a Pear cut.

Octagon cut

The standard number of facets of an Octagon cut gemstone is 53. This is another “step” cut but with the four corners mitred. The facets run in steps parallel to the gemstone circumference. This cut is differentiated from the Emerald cut by steps on the pavilion that are not equidistant.

With this cut, colour plays a very important role in the beauty of the gemstone as colour tends to show very dramatically in Octagon cut gemstones.

Emerald cut

The approximate number of facets of an Emerald cut gemstone is 50. The Emerald cut looks like a rectangle from the top, with truncated corners. These can be beautiful gemstones with stepped facets; the sheen tends to display large flashes of these stepped angles on the pavilion of the gem.

This is another “step“ cut and it has rows of facets that resemble a staircase and usually are four-sided or elongated. It is known as a step cut because its concentric, broad, flat planes resemble stair steps.

The Emerald cut is differentiated from the Octagon cut by its equidistant steps on the pavilion. The flat planes of the outside edges allow for a variety of shapes. Generally, the length-to-width ratio should be 1.5:1 to 1.75:1.

With this cut, colour plays a very important role in the beauty of the gemstone as colour tends to show very dramatically in Emerald cut gemstones. The Emerald 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.

Marquise cut

The standard number of facets of a Marquise cut gemstone is 57. The Marquise cut is also known as the “Navette” shape and looks like a long oval that has been stretched out to a point at each end like a rugby ball viewed straight down from the top.

The general ratio of length to width should be 2:1. It is important that the Marquise cut gem not be too shallow or light will pass through the back of the gem diminishing its brilliance and colour. However, as with all coloured gems, this can vary from type to type.

The Marquise cut provides good brilliance and colour and is gorgeous when used as a solitaire or when enhanced by smaller gems.

The Marquise cut was inspired by the fetching smile of the Marquise de Pompadour and commissioned by the Sun King, France’s Louis XIV, who wanted a Diamond to match the smile.

Antique cushion cut

Antique is from the Latin word “antiquis”, meaning “classic” and is a primary cut first used on Ruby and Sapphire faceted in Sri Lanka.

The approximate number of facets of an Antique Cushion cut gemstone is 64 and it is also known as “The Old Miner” or “Old European” cut because it looks like a cross between a deep cut with large facets that was common in the late 19th and the early 20th centuries and a modern Oval cut. As it looks somewhat like a sofa cushion, the word “Cushion” is typically used in combination with “Antique”, but generally only when the sides are equidistant.

This shape is also sometimes referred to as the “Pillow” cut (for obvious reasons) or the “Candlelight” cut in reference to cuts designed prior to electric lights, when gems sparkled in the light provided by candles. It has a marvellously romantic and classic look that stands out from other cuts and along with the Princess cut, the Antique Cushion cut maximises a gem’s lustre.

Princess cut

Technically known as the “Square Modified Brilliant” cut, the Princess cut is a square version of the Round Brilliant cut with 76 sparkling facets.

Depth percentages of 70% to 78% are not uncommon in the Princess cut and it is a “Brilliant Style” shape with sharp, uncut corners (“Brilliant Style” refers to the vertical direction of the crown and pavilion facets).

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 maximise 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.

The Princess cut generally works best with lighter coloured transparent gemstones and along with the Antique Cushion cut, the Princess cut maximises a gem’s lustre.

The Princess cut was designed for weight retention of octahedral Diamond crystals, helping to create more attractive Diamonds at more reasonable prices. The Barion cut was the forerunner of the Princess cut and was invented about 30 years ago by Basil Watermeyer of Johannesburg. The Barion cut has been the subject of patents that have expired within the past ten years and this has led to the greater availability of similarly cut gemstones. The style we now know as the “Princess” cut has since become a generic style of cutting. According to Harold Newman’s “Illustrated Dictionary of Jewellery”, the term “Princess” cut was previously applied to what is now known as the “Profile” cut developed by Arpad Nagy of London in 1961.

Heart shape cut

The standard number of facets of a Heart Shape cut gemstone is 59 and is a pear-shaped gemstone or Diamond with a cleft at the top. Generally, a Heart Shape’s length to width ratio is slightly over 1:1, approximately 1.1:1 in favour of length, but usually not over 1.2:1.

The ultimate symbol of love, most Heart Shape cut gems are nearly round. This has the advantage of having a nearly round pavilion that provides beautiful brilliance. Most Heart Shape cuts are purchased as single gems. Solitaire rings are set with hearts throughout the range of sizes. After necklaces and rings, most Heart Shape cuts are sold as matched pairs for stud earrings. The primary market for Hearts is for luxury jewellery and there is heavy interest in the Heart Shape cut in the Far East.

Hearts must be extremely well cut which makes them more expensive because excellent proportions result from a greater expenditure of rough. Understandably, noticeable increases in sales of Heart Shape cut gems occur around Valentine’s Day. As with all Fancy cuts, buyers of Hearts should look first at the overall make. The first question to ask is, “Do I find the gem pleasing to the eye?”. Generally, look for a balanced shape, avoiding extremes. Lobes should be rounded, and the cleft should be relatively sharp and distinct.

Briolette cut

The Briolette cut is believed to derive its name from the French words “Brilliant” (brilliant or sparkling) and “Brignolette” (a small dried plum).

The Briolette cut is 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 cut and polish 5-10 Briolette gemstones per day. Because of the specific number of cuts to show the facets, the Briolette cut requires perfection from top to bottom. While the approximate number of facets of a Briolette cut gemstone is 84, the more facets the drop has, the more brilliant it is.

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 rumours 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 coloured gemstones. Most Diamond Briolettes are cut from white rough, but coloured Diamond Briolettes, especially Fancy and Canary Yellows, are becoming more popular, followed by Cognacs and Champagnes.

Briolette gems are found in antique tiaras and estate jewellery from the Victorian, Edwardian and Art Deco eras. Today, Briolette gems are increasing popular in fashion jewellery. 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.

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.

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 jewellery was made with Cabochons, including astounding Royal East Indian jewellery and the breastplate of Aaron.

Cabochons are used for making jewellery, 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 centre of the gem. The cut shows good brilliance and has a crown that is less easily abraded than those of faceted gems.

Millennium cut

Possessing an incredible 1,000 facets, the Millennium cut is so named as it was created by Rogerio Graca around 1999 as a unique and challenging symbol of the new millennium.

While sometimes confused with the Concave cut, the Millennium cut is easy to spot as it creates a gem packed full of facets.

One Millennium cut gem equates to approximately 18 times the amount of work of other cuts. Having 624 facets on the pavilion and 376 facets on the table, each facet has to be touched from one to four times during cutting and polishing.

The amount of time involved, combined with the design particularities (rough selection, keeping a degree of sharpness between each facet, making enough space for each facet etc.) and the need for precision machinery, eliminates the possibility of the Millennium cut ever becoming mainstream.

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 colour and light is always the first consideration in cutting gems, 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 labour required.

Mirror cut

The Mirror cut is characterised 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”.