A gemstone is a mineral or rock, which can be used in jewelry after cutting or faceting and polishing. Gemstones are an important commodity in today’s marketplace. They have been sought after for thousands of years for their beauty, metaphysical properties, and commercial uses. In earlier times there were no such things as synthetic gemstones but today they are quite common.
Gemstones are diverse in their beauty and many gems are available in a stunning variety of colors. Most gemstones have little beauty in the rough state. They may look like ordinary rocks or pebbles. After a skilled cutting and polishing of a gem, full color and luster can be seen.
On the basis of its formation, gemstones are classified into five categories:
These have been formed in natural environment with no interference by human. They form in a variety of ways in many different environments from many different chemical compounds. By the time they appear in our jewelry they’ve been cut or polished, but they’ve not been treated or altered in other ways.
Genuine Gemstones are nothing but natural gemstones which are treated in some way to enhance its appearance. A large percentage of natural gemstones are treated to enhance their appearance for jewelry manufacturing.
A synthetic gemstone shares a natural stone’s physical, chemical and optical qualities, but it is created in a laboratory. Now-a-days, synthetic versions of nearly all popular gemstones are available. Some modern synthetic gemstones look more natural and are more difficult to identify, but an experienced jeweler or gemologist can usually detect them. Jewelry that includes quality synthetic gems can be just as beautiful as jewelry made with natural stones.
Imitation or Simulated Gemstones
Imitation gemstones can be anything that resembles a natural gemstone but does not have the same physical characteristics or chemical composition. These items are usually much less expensive than the natural forms. Imitation stones are often made of glass or plastic and most can be detected easily by a jeweler.
A number of techniques are used to improve the color and appearance of natural and synthetic gemstones. Gemstone’s beauty is enhanced, to increase the desirability and demand of the gemstone. Probably the oldest method is that of heat treatment for gemstones to improve or change the color. As a result of recent advances in technology, there are now many different techniques, which use modern equipment such as lasers, and computer controlled heating and irradiating procedures. Lasers are used to drill holes into stones to reach inclusions. These are then evaporated or removed using chemicals before the crack is filled. Some treatments are permanent such as drilling while others maybe temporary. For example stains and fillings may leak, some heated, and irradiated stones may fade or revert to their original color.
Gemstones are categorized similarly to diamonds as far as pertaining to cut, clarity, and size. The color, however, is broken down into three parts:
The most valuable gemstones are those that exhibit a pure color and only “slight” hues of other colors in addition to their primary color, For example, sapphires range in hue from “slightly purplish-blue” to “slightly greenish-blue,” pink sapphires always range from “pink” to “slightly purplish-pink,” and rubies range from “slightly orangish-red” to “slightly purplish-red”.
Tone represents the depth of color, ranging from colorless to black. Gemstone tone is described as “light,” “medium-light,” “medium,” “medium-dark,” and “dark.
Saturation, or color purity, refers to the degree to which the gem is free from brown or gray hues. The most desirable gemstones, which show little gray or brown, are often described as having “vivid” or “strong” color saturation.
The other characteristics of colored stones are:
Similar to diamonds, a gemstone’s weight is also measured in carats where one carat equals 200 milligrams. However, in case of gemstone, this may not give an accurate idea of its size, because different types of stones have different densities Two gemstones of the same carat weight may be different in sizes. For example, a 1 carat Sapphire or Ruby will be smaller than a 1 carat Emerald, though they have the same carat weight, because Sapphires and Rubies are denser than Emeralds. At the same time, a 1 carat Diamond will be larger than a 1 carat Ruby as a Diamond is less dense than a Ruby. Gemstones can also be measured in dimensions (diameter, length, and width).
A good cut is something that may give a gemstone its beauty and brilliance. A gemstone’s cut refers to its proportions and symmetry. The stone should be symmetrical in all dimensions so that it will appear balanced, and so that its facets will reflect light evenly, which will provide good brilliance to stone. A well- cut faceted gemstone reflects light back evenly across its surface area when held face up. If the stone is too deep and narrow, surface area will be dark and if it is too shallow and wide, parts of the stone will be washed out and lifeless.
While cutting, color of a gemstone should also be taken into account for optical efficiency. If a stone’s color is highly saturated, a shallow cut will allow it to pass more light, while a deeper cut may increase the vividness of a less saturated gem. There is no generally accepted grading system for gemstone cut.
Clarity is a term used to describe the absence or presence of flaws inside or on the surface of a gemstone. A flawless gemstone is rare and usually expensively priced. Most gemstones have inclusions, or tiny mineral flaws, that can be seen under magnification or by the careful eye. A gemstone may have inclusions, cracks, spots, clouds, or any other blemish or imperfection.
Clarity is a key factor in determining quality and the value of a gemstone. Inclusions not only distract the eye, but interfere with the behavior of light in the gem, and have a significant affect on brilliancy or sparkle. Generally most minerals contain inclusions and spots but if they do not affect the durability of colored gems then these inclusions or spots will not devalue much for the gems except diamond.
For diamonds, Clarity Grade Scale from F (flawless) to I3 (included 3) is used whereas for other colored gemstones a different grading scale is used. Colored stones have different habits of clarity, so that they are classified into three ‘Types’, which are defined as under:
Type I colored stones include stones with very little or no inclusions. This category can include Aquamarine, Blue Topaz, Zircon, Morganite, Tanzanite, etc.
Clarity in the Type I group is classified as VVS (minute to detectable), VS (minor), SI1 (noticeable), SI2 (obvious) or I (included)
Type II colored stones include stones that often have a few inclusions. This category can include Corundum, Garnets, Iolite, Peridot, Quartz (Amethyst, Citrine, Ametrine), Ruby, Sapphire, Spinel, etc.
Clarity in the Type II group is classified as VVS (minor), VS (noticeable), SI1 (obvious), SI2 (prominent), or I (prominent, affecting appearance).
Type III colored stones includes stones that usually always have inclusions. This category can include Emeralds, Tourmaline, etc.
Clarity in the Type III group is classified as VVS (noticeable), VS (Obvious), SI1 (prominent), SI2 (more prominent), or I1 (affecting appearance or durability).
Gemstone Enhancement is a treatment process other than cutting and polishing that improves the appearance (color / clarity), durability or availability of a gemstone. This treatment covers heating, oiling, irradiation, waxing, dying, bleaching etc.
There are many ways to enhance the appearance and durability of gemstones. Some of these treatments or enhancements, are permanent where as others are temporary. Gemstone enhancement has become such a common as well as accepted practice that experts believe the vast majority of stones are treated in some way. It’s important to remember that most gemstone enhancements greatly improve the appearance – and hence the value – of a stone.
All gemstones can be divided into 3 basic categories:
- N – The ‘N’ symbol appears on the chart only for natural stones which are not currently known to be enhanced.
- E – The ‘E’ symbol appears on the chart only for those gemstones, which are routinely enhanced. The type of enhancement covered by this symbol is indicated on the following chart.
- Third category covers those gemstones which are treated in a non- traditional manner and that enhancement process or code is not covered under ‘N’ & ‘E’ symbols.
Chart for Gemstone Enhancement Information
B- Bleaching: The use of chemicals or other agents to lighten or remove a gemstone’s color. Pearls and ivory also may be bleached to lighten their color.
C – Coating: The use of such surface enhancements as lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color or add other special effects.
D – Dyeing: The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.
F – Filling: As a by-product of heat enhancement, the presence of solidified borax or similar colorless substances which are visible under properly illuminated 10X magnification.
G – Gamma/Electron Irradiation: The use of gamma and/or electron bombardment to alter a gemstone’s color; may be followed by a heating process.
H – Heating: Heating is one of the most common treatments used to enhance the natural beauty of colored gemstones. It is a permanent process that can dramatically improve the color and/or clarity in a number of stones, including sapphires, rubies, diamonds, aquamarine, amethyst, tanzanite, topaz, tourmaline and other stones.
I – Infilling: The intentional filling of surface breaking cavities or fractures usually with glass, plastic, opticon with hardeners and/or other hardened foreign substances to improve durability, appearance and/or add weight.