The world of colored gemstones is enticing and beautiful. Minerals formed deep within the earth are brought to light and then expertly fashioned by lapidarists into coveted and prized treasures. Gem cutting is an art, a collaboration between man and nature. And while no two people perceive color in the exact same way, read on to gain expert knowledge on how important criteria such as cut and color impact a gemstone’s price.
What is color in a gemstone?
There are three major factors that determine the Color of a gemstone. These principles are :
- Hue. This is the main color that the eye perceives. Gemstones will often have a dominant body color as well as a secondary color. Descriptions of hue would include a reference to the dominant and lesser body color, such as “orangey-red” or “greenish-blue.”
- Saturation. Also known as chroma, saturation refers to the intensity of the color and is described on a scale of high to low using terms such as vivid to describe intense saturation and grey to describe low color saturation
- Tone. Tone refers to how dark or how light the color of a gemstone appears. It is rated on a scale of 0-10 from light to dark. 0 would be colorless, and the distinctions progress from very, very light, to very very dark.
There are thirty one accepted descriptive gemstone hues that range the entire color spectrum from red to violet and the varieties among different color combinations in between. The most valuable colored gemstones will have vivid color saturation and fall in the middle of the hue and tone grading scales. There are specific vivid hues considered highly desirable in different gemstones. Some of the color descriptions you will see include “cornflower blue” when describing blue sapphires, “grass green” when describing emeralds, and “pigeon’s blood red” when describing rubies. These color descriptions are meant to communicate the most valuable hues in precious gemstones.
Color in gemstones is prized, but color in diamonds is often described as the lack of color. The exception to this occurs when the saturation of color in a diamond is so intense, that it is considered desirable. Aside from irradiated colored diamonds, most color in diamonds and gemstones is caused by elements and gasses present when the stones are formed. These diamonds are called fancy colored diamonds.
What are the types of gemstone cuts?
Gemstones come out of the earth in a rough crystal formation. Each mineral will have its own unique arrangement and structure. It is up to the gem cutter, or lapidary, to bring out the inherent beauty. Some of the most well-known gemstone cuts are:
- Cabochon: a cabochon or “cab” can be cut to a variety of shapes and has smooth surfaces without facets.
- Round and round brilliant; this typically has 58 facets, or polished surfaces.
- Princess cut: square shaped with angular facets.
- Cushion: this has a square or rectangular shape but with slightly curved sides and soft edges.
- Radiant: this is rectangular with cut corners and angular facets.
- Emerald cut: this differs from the radiant in that it is rectangular with cut corners and parallel facets.
- Asscher cut: a modified emerald cut, in that it is square with cut corners and parallel facets.
- Trillion, which is triangle shaped.
Some gemstone cuts are fairly self-explanatory, as the name gives the indication of the general shape.
- Heart
- Oval
- Pear
- Marquise
Check out this image to see some of these cuts and a comparison between round, radiant and princess cuts of a diamond. While cabochons do not have faceted surfaces, most other gemstone cuts will. The largest facet is called the table. Surrounding the table are star facets, then bezel facets, and upper girdle facets. The girdle or outer diameter of the stone may or may not be faceted. The area below the girdle is called the pavilion and may have parallel or kite shaped facets. The very bottom of the stone is called the culet, which may or may not be polished. Sometimes there is no culet. When the gemstone does not terminate to a single point, it may have a keel.
When questioning why a lapidary might or might not facet a girdle or make any other curious cutting decisions, the answer is almost always the same: to maximize the weight and/or color of the gemstone. A well cut gemstone will have a pleasing symmetry and a good length to width ratio (if the stone is not round). Click to learn more about how an expert cuts and polishes gemstones from Jeff – an AGTA award winning lapidarist.
Let us hear about your favorite gemstone cuts. Is there a certain color you associate with a particular cut? We want to know about it. In the mean time – learn more about how to buy gemstones.