What’s in a Rock

Gemstones - What’s in a Rock

Gemstones : Using the Four C’s to size up a gemstone

If you`ve considered following in the footsteps of Bluebeard or the Queen Mother by sinking your assets into gemstones, you probably already know that not all gems of a certain type are equal, or even particularly valuable.

Dealers may use different grading systems to determine those values, but they are all based on the four C`s: the stone`s carat weight, its degree of clarity, its color, and the skill with which it was cut. Richard Drucker, publisher of an international wholesale price list called the Guide, here explains the various factors that go into determining a gem`s worth.

Cut: This is the only factor determined by the cutter and not by nature. A gemstone is like a tiny prism – the slightest change in the angle of a cut will affect how it refracts light – thus the « fire » in a ruby can only be released by a skilled cutter. A well-polished gem will be far more radiant and, therefore, far more valuable.

Color: Color quality is determined by the gem`s actual color (hue), how rich the color is (saturation), and how light or dark it is (tone). This is “by far, the most important factor affecting price,” Drucker says. “Slight differences in color may mean great differences in price.” Unfortunately for the beginner, judging color is a highly subjective process, and one that requires a practiced eye to find the perfect saturation of green in an emerald.

A lady with gemstones. Photo by Elena

Carat weight: Gemstone weight traditionally was measured with carob seeds, which weigh about one-fifth of a gram. Today`s standard measure, the carat, sprouted from the carob seed both etymologically and physically – one carat eqeuals 200 milligrams, or one-fifth or a gram.

Remember that the increase in a gemstone`s value is not linear. A half-carat ruby might cost $55, but a one-carat ruby of the same quality might be $150, simply because larger rubies are harder to come by or, as Drucker says, “because it has more intrinsic value to say you own one carat of something.”

Clarity: Nothing is perfect, but the closer to flawless a gemstone is, the more valuable. In this case, a flaw refers either to tiny mineral deposits, which are called inclusions, or to fractures in the stone, which are called cleavages. Some gems, like emeralds, are more likely to be fractured and are thus grades more leniently.

Fact File: What`s your stone The origins of ancient birth-stone designations are lost to history, but we know modern birthstones were designated not by a poet or some other qualified stone interpreter, but by a jeweler`s association. They may have been concerned about the limited availability of some gems.

•     January: Ancent and modern : Garnet
•     February: Ancient and modern: Amethyst
•     March: Ancient – Jasper, Modern – Bloodstone, aquamarine
•     April: Ancient – Sapphire, Modern – Diamond
•     May: Ancient – Agate, Modern – Emerald
•     June: Ancient – Emerald, Modern – Pearl, Moonstone, Alexandrite
•     July: Ancient – Onyx, Modern – Ruby
•     August: Ancient – Carnelian, Modern: Carnelian, Peridot
•     September: Ancient – Chrysolite, Modern – Capphire
•     October : Ancient – Aquamarine, Modern – Opal, Pink Tourmaline
•     November: Ancient – Topaz, Modern – Topaz, Citrine
•     December: Ancient – Ruby, Modern – Turquoise, Zircon.

Gemstones. Photo by Elena