If you have ever shopped for a gemstone, you have no doubt encountered the Four C’s. The Four C’s were developed by the Gemological Institute of America in the 1940’s to 1950’s as a means to communicate to the diamond buying public the four major value determinations that affect a diamond’s price. The efficacy of the 4 C’s in communicating this material was so successful that is has been appropriated to describe gemstones of many varieties, not just diamonds.
Carat: Size Does Matter
Gemstone weight is expressed in carats. One carat is the equivalent to 200 milligrams. Gemstone sizes are frequently communicated in millimeters if the gemstone is small, typically less than one carat. Since gemstones do not all have the same specific gravity, carat weight is not a standard measurement of dimension. Variations in gemstone density mean you will see different gems that have the same carat weight but have very different sizes. Larger gemstones occur much less frequently in nature than smaller ones. Due to the rarity of large gemstones, the higher the carat weight, the higher the price per carat will be.
Cut: The Shape of Things
Cut not only refers to the silhouette of the gemstone, but also the quality of the cutting itself. Gems are frequently carved for decorative ornamentation, faceted with parallel or kite-shaped facets, or cut en cabochon, smooth surfaces with no angular faceting. A fine cut gemstone will have a pleasing symmetry, well-defined facet junctions if facets are present, and smooth polished surfaces. Colored gemstones are also cut to preserve color and to maximize carat weight. Many gemstones will exhibit zones of color that a skilled lapidary will take into careful consideration and make the best use of. An excellent cut can accentuate color and show a gemstone at its best, while an inferior cut can destroy a gemstone’s color.
Clarity: A Complex Element
Clarity refers to the purity of a gemstone and is a way to describe the “fingerprints” of nature that take many forms internally and on the surface of gemstones. In precious gems, a high clarity grade means transparency of the gemstone, allowing the full beauty of gemstone color to be realized without interruption or interference by natural inclusions in the crystal structure. Gemstones are transparent, translucent, or opaque. Many gemstones that have characteristically low clarity, such as emeralds, can be highly valuable. And semi-precious gemstones are frequently valued for their interesting and unusual inclusions.
Color: A Subjective Field
While carat weight, cut, and clarity are easy to define, the way a gemstone’s color impacts its value can be a very subjective field. How we perceive color depends on how a gemstone absorbs and reflects light. While GIA recognizes over 30 distinct descriptions of gemstone color, or hue, it also lists ten gradations in tone,(from light to dark) and specifies six levels of color intensity (neutral to vivid). Furthermore, it is common for gems to exhibit two or three hues, sometimes all at once. In many cases, gemstone color can come down to personal preference. Color is evaluated and described in these in three ways: hue (the dominant color that you see), saturation (the intensity of that color), and tone (how light or dark the color appears). And since no two people perceive and appreciate color in the exact same way, desirable color in gemstones owes a lot to personal preference.
You can continue through our tutorials for more in depth information about the Four C’s. By now, you have a basic understanding of how these factors are used to evaluate and describe gemstones. Would you like to know more? Post your questions and comments about the Four C’s and we will direct you to comprehensive details that will broaden your gemstone knowledge.
Read other posts from the Introduction to Gemstones series.