Step 1: Introduction to Gemology
Table of contents:
- The Three Basic Gem Cutting Styles
- Brilliant Cut
- Step Cut
- Mixed Cuts
- Shape and Style Combinations
- Rose Cut
- Briolette Cut
- Ceylon Cut
- Barion Cut
- Modified Cuts
- Cabochon Cuts
- Named Cuts
- Portuguese Cut
- “No Name” and “New Name” Cuts
- Curved Facets
- Fantasy Cut
- Concave Facets
The Three Basic Gem Cutting Styles
Brilliant cuts consist of triangular and kite-shaped facets that spread outward from the center of the gem. As befits its name, the brilliant cut gives off the most scintillation of any cut.
Step cuts consist of rectangular facets that ascend the crown and descend the pavilion in steps. Examples of step cuts include emerald and baguette cuts. These are popular because they show off the stone’s color and clarity and produce a subtle gleam.
Mixed cuts combine step cut and brilliant cut styles. They have brilliant facets on the crown and step facets on the pavilion, or vice versa. Mixed cuts may even combine cabbing and faceting techniques.
Shape and Style Combinations
Faceters can combine the above cutting styles with almost any shape. For example, a square modified brilliant is a princess cut. A square step cut with beveled corners is an Asscher cut. A square mixed cut is a Barion cut.
Of course, you can also find variations within all shapes. A triangular gem can have many or few facets, much or little brilliance and scintillation, etc.
While brilliant and step cuts currently enjoy the most popularity, the rose cut is a unique style important to gem-cutting history. Dating back to the 16th century, the rose cut has a round, cabbed flat base and a faceted top. (Occasionally, you’ll see a gem with a faceted pavilion and a domed crown. However, this isn’t a standard cutting method).
Triangular facets rise to form a shape like a faceted mound. While the number of facets on each rose cut varies, the face-up shape is almost always circular. For 16th-century cutters, roses maximized the use of flat rough and created gems with more brilliance than previously seen.
However, this cut gives little fire. It’s not nearly as bright as a modern brilliant. Over subsequent centuries, many jewelry owners had their rose-cut diamonds recut into more fashionable shapes. Of course, fashions do turn. Rose cuts are now making a comeback due to their vintage appeal.
Another notable vintage cut, the briolette is a faceted teardrop. It also resembles a fully rounded pear or a double-rose cut. During Victorian times, jewelers often drilled these then-popular gems to use as beads for pendants and earrings.
The Ceylon cut has a step-cut pavilion and a brilliant-cut crown. This ancient technique is still used in Sri Lanka. Studies have shown that the reverse, a step-cut crown over a brilliant-cut pavilion, will often produce the greatest brilliance.
While a mixed cut, the Barion cut also deserves a category of its own. Essentially, it places a round brilliant pavilion into a fancy shaped gem. It usually has a step-cut crown as well. This typically results in far greater brilliance than other methods. However, Barion cuts can come in almost any shape and vary widely in their facet arrangements.
Some have brilliant facets on both crown and pavilion, while others have step cuts on the crown and brilliant cuts on the pavilion. Their unifying feature, which separates the Barion from mixed cuts, is the quarter moon facets located directly beneath its girdle.
The arrangement of Barion-cut facets also creates a characteristic cross-shaped pattern at the center of the stone. Barions eliminate the bowtie extinction effect. Also, since they tend to be deeper than other cuts, they allow cutters to maximize rough and concentrate on color.
Barions with round brilliant pavilions, compared to other pavilion shapes, offer greater light discipline inside the gem. Such a gem can display a striking “fountain of light” effect.
Gem cutters can modify brilliant, step, and rose cuts to maximize use of rough or create interesting effects. The shape and facet types remain the same, but the number and arrangement of facets may differ.
If cut differently from the standard, gems have the term “modified” added to their names. For example, “modified round brilliant” or “modified emerald cut.” The Barion is an exception to the “modified” rule, because its name already embraces a variety of facet placement styles.
Please note that gem cuts in the brilliant style are always called brilliant cuts (for example, “round brilliant”), while gem cuts in the step style generally have specific names attached to them (for example, Asscher or emerald cuts).
Gems polished into domes are called cabochons or cabs. These types of gems date back to ancient times and have remained popular in the centuries since.
Lapidaries cab certain gem species, such as opal and moonstone, to better display visual effects such as play of color, cat’s eye, and asterism. In faceted gems, these effects would be less visible. Some stones may be cut into cabochons because they’re lower quality or too opaque for faceting. Cabbing these stones would emphasize their color and luster rather than brilliance. Softer gem materials may also receive cabochon cuts, since cabs don’t show scratches as easily as faceted gems do.
Cabochons usually have circular or oval shapes. Sometimes, gem cutters may give them square or rectangular shapes. In those cases, they will show creases. Cabochons can be single cabs or double cabs. Typically, natural stones are polished into double cabochons to maximize weight.
New gem cuts are created every day.
In a checkerboard cut, a faceter cuts the gem with square facets, so its crown and table resemble a checkerboard. This cut is often used on translucent stones.
The divine cut, a round cutting style, allegedly gives a gem more sparkle, a higher perceived color grade, and a larger face-up appearance than round brilliants.
The snowflake cut is another refreshingly beautiful new design.
As a group, these creative but less frequently seen cuts are known as named cuts. As technology advances, the number of named cuts increases. Gem lovers will always drive innovation. However, not all named cuts are new.
A traditional named cut, the Portuguese cut has several tiers of facets, which create a wonderful display of light. It has more scintillation than almost any other cut. As you can see from the photo below, the Portuguese requires many facets and considerable labor. These factors, in addition to the fact that the rough must have greater than normal depth, ensure that you’ll only see this cut occasionally.
“No Name” and “New Name” Cuts
Some cuts have no name at all. Sometimes, faceters simply use a cut that fits a piece of rough, something that just “works.” The red gem below is a good example of this. It’s a simple cut with a radiant pavilion.
When the GemCad program was released in the 1980s, people were able to test their gem cutting designs on a computer before taking a stone to a lap. This made it easy for people to create new cuts. Today, there are thousands of new designs. Many of these newly named cuts are simply a means to standardize common techniques. For example, someone may “design” the cut used on this red gem and save it with a computer program. They then have an established method for cutting it that can be referenced and used again. What was once a “no name” cut that just worked for one stone can now become a “new name” cut that could work with other stones.
While most newly named cuts are just variations on standard cuts, some are unique. Indeed, there seems to be no end to the imagination of our lapidaries. There’s no limit to shapes or the number and arrangements of facets. Some new cuts are merging a variety of techniques. Below is a Barion cut gem with a parallelogram outline.
Flat facets aren’t the only gem cutting technique available to today’s lapidaries.
A fantasy cut is a popular style of faceting. This technique uses large pavilion facets. Some simple grooves are used, which are mirrored throughout the pavilion. This ametrine is an excellent example of a fantasy cut gem.
Hand cutting isn’t the only way to make precise, concave facets. There are now faceting machines that can accomplish this. The gems are first cut traditionally with flat facets. Then, they’re transferred to another machine for an additional set of concave facets. However, the extra labor required for this is so considerable that this technique is unlikely to see widespread use. Nevertheless, as you can see from the picture below, the results are nothing short of spectacular. The brilliance and scintillation exceeds anything that can be done with flat facets alone.
There is no end to what a lapidary can do with gemstones. Keep your eyes open and you’re sure to see cuts that are totally unique.