Gemstone Inclusions: The Good, the Bad and the Ugly
The definition of perfect, according to Merriam-Webster, is to be "entirely without fault or defect". So in essence, in order to be defined as perfect, something must be internally and externally flawless. A natural gemstone is nature's creation and most of us are all too aware that nature is rarely perfect. It is fair to say that natural gemstones are expected to have some degree of imperfection, allowing the concept of flawlessness to flow with leniency in the colored gem trade. Colored gems have completely different standards to diamonds, with regard to what are acceptable inclusions, which is why the colored gem trade lacks an official clarity grading scale.
Gemstones can have both external and internal flaws. Gemstone flaws occurring on the outer surface of a gem are more than likely the result of an "external" environmental factor. Some examples of external flaws commonly found with precious gems are scratches, blemishes or chipped edges. These kinds of surface flaws may affect the value and appearance of a gemstone, but other types of external flaws, such as natural flaws, may not affect a gemstone's value.
Internal flaws found in gemstones are known as inclusions. Gemstone inclusions are often used to help identify a specific gem. Like fingerprints, each gemstone has its own unique internal structure. Due to the individual characteristics of each gem, no two gemstones are alike. Whether it's the weight, dimensions, color, purities or impurities, a gemstone is unique as a snowflake. Formed by nature, or sometimes by man through the process of enhancement, inclusions can make the most intriguing of gems even more uncommon. Internal gem inclusions can be classified in several ways, but will generally fall under one of the following main categories:
A solid inclusion is any enclosed inclusion, which can pretty much mean any other mineral specimen, including the host mineral. For example, solid inclusions can include pyrite deposits found in lapis lazuli, green mica deposits in aventurine and rutile deposits found in sapphire. Other solid inclusions could be needles, minerals and crystal growths such as calcite.
Some gemstone specimens have unique internal cavities within their structure. Typically these cavities are very small, but some specimens may have quite large cavities. These cavities are often occupied by a liquid, such as water or saline. Cavities can also contain liquid carbon dioxide or even natural hydrocarbon compounds. Topaz, beryl and quartz are gem types known to have frequent occurrences of liquid inclusions and opals have an extremely high water content, sometimes up to 30% liquid silica gel or hydrated silicon dioxide. This liquid is responsible for producing the vivid rainbow hues in opal's play of color.
As with liquid inclusions, gaseous inclusions are gasses that occupy a cavity within a gemstone. Typically cavity gasses are composed of air, but they can also be filled with carbon dioxide or compound gasses. It is even possible for gasses to be within a liquid inclusion as well. Gaseous inclusions can be easily identified since they appear as bubbles in a gemstone.
One type of optical illusion is where the host crystal's external shape can be seen in a gemstone. As a host crystal grows, stops, and then starts to re-grow again, it coats previous surface layers. During this repeated process, preexisting layers are coated with new substances. The resulting formation is what is referred to as a phantom inclusion. Another type of optical inclusion is caused when changes in the structure or composition of a crystal result in color zoning. Additionally, radiation halos are caused by radioactive minerals in crystals.
It is understandable to believe the common misperception that all inclusions are bad, especially since the very word, inclusion, can easily conjure up vivid images of nasty internal cracks, feathers, fractures or clouds, but the truth is that not all inclusions are bad. In fact, there are even some gem types that are actually valued for their inclusions. For example, amber is a gem type composed of fossilized, hardened resin. Insects, plants and other organic materials are often found trapped within the resin, and specimens with organic matter inside are highly prized and valued. Other types of gems with valuable inclusions are rutile quartz, Russian demantoid garnet and certain types of corundum, such as ruby and sapphire that contain velvety rutile inclusions (known in the trade as "silk").
It is fair to say that the value of a gemstone is based on its rarity and not whether or not it has so-called flaws. A gemstone with impurities and inclusions may actually be considered a perfect specimen and could just be more valuable than you would expect. Therefore, please carefully consider disregarding included gems, because they could turn out to be more valuable than one would think.
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- First Published: September-01-2012
- Last Updated: June-22-2017
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