Buying a natural gemstone is not as easy as it looks. Determining the quality of a gemstone is one of the most important things customers must do before buying a gemstone.
The appearance of colored gemstones is a combination of many separate factors, each of which is related to, and affected by, the others.
While there are no officially accepted systems for grading colored gemstones, these are certain criteria taken into consideration when determining the quality of a natural gemstone.
To determine the quality of colored gemstones, experts rely on four criteria: Color, Cut, Clarity, and Carat.
1. Color
The appearance of a colored gem is a combination of many separate factors, each of which is related to, and affected by, the others.
Look for stones that look good even under the low lighting conditions you find in the evening or in a restaurant, for these are typically the conditions under which fine gems are worn and viewed.
Color is the most important factor in determining quality and Gemologists usually describe gem color by referring to three properties:
- Hue position
The basic hues are red, orange, yellow, green, blue, violet, and purple. Black, white, and brown refer to tones and saturation, not hues.
- Saturation
A gem’s saturation refers to the intensity of its hue. Colours can be strong or soft.
- Tone
A gem’s tone refers to a gem’s relative lightness or darkness. Black and white are tones, from darkest to lightest.
2. Cut
Even the most exquisite of gemstones, when excavated, are rough and comparatively unattractive. A gemstone requires cleaning and cutting to gain a resplendent form.
A stone cut into a variety of square facets with regular spaces around is known as Checkerboard cut. It is common in garnets, topaz, citrines and amethysts or other semi-precious stones.
Characterised by a rounded top and flat bottom 'Cabochon cut' is common in gems like star sapphire, cat's eye gemstones, tiger's eye gemstones, star gemstones and star ruby.
Rose Cut is one of the varieties of cabochon cut where flat facets are polished into the curved area of cabochon cut stone.
3. Clarity
Gemstones contain a wide variety of inclusions. In case of the faceted gems, inclusions are that will interfere with the free passage of light through th. These can include little bits of minerals, hollow areas, and fractures. Clarity grading addresses the visual and structural impact of these things.
Clarity can be judged by reference to the overall inclusions. Magnification can be used to locate inclusions, but with the exception of inclusions which might impact durability, only those visible to the naked eye should be considered in the final grade.
They may look beautiful at the first glance, but fractures and veils go deeper into the gem. Pay special attention to these inclusions. They are considered a weakness in the gemstone, which may be prone to breakage.
4. Carat
A carat is a unit for measuring the weight of a gemstone. One carat equals 1/5 of a gram, or 200 milligrams. However, neither weight nor size determines the value of any gem.
Everything else being appropriate, the larger the gemstone, the more valuable it is. For example, fine quality rubies weighing over one carat are very rare and thus more valuable.
In most gemstones, per-carat prices tend to increase with carat weight. You can expect steep increases in the price per carat at the one, three, five, and ten-carat levels.
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