The Fun of Gemstone Inclusions
Gemologists call them ''inclusions''--not ''flaws''--for a reason.
They're not the same thing at all.
Inclusions vs. Flaws
Inclusions, especially in colored gemstones, are part of and often add value to natural stones. While avoiding inclusions is certainly advisable with regards to diamonds, clarity grading for other stones is significantly different. Among transparent gemstones--especially the cardinal stones of ruby, sapphire and emerald--inclusions are not only proof of naturalness, but certain forms add rarity and value to a stone.
Gemologists use the word "inclusion" as a label for foreign matter, or structural irregularities, in the makeup of a specific gemstone. Inclusions can be crystals of other materials, enclosed bubbles of liquids or gasses, organic materials and other differences.
Common Inclusions That Add Value
Here is a list of commonly included gemstones, with a description of their inclusions, and how they add value to the material:
Inclusions in natural amber--especially organic inclusions--can cause a specimen's value to skyrocket. An amber cabochon, its golden color from fossilized tree resin, is beautiful. An amber cabochon, with a fragment of dinosaur feather or prehistoric ant encased inside, is precious beyond compare.
Inclusions in emerald--in almost every member of the beryl family, actually--are common and expected. In emeralds, these inclusions are called "jardin" (French for "garden"), and they are used to determine that a stone is natural (not synthetic). Certain forms can also help gemologists determine an emerald's source, as they can be indicators of a deposit's formation.
As with emeralds, inclusions can tell gemologists and collectors about the origins of a garnet. A horsetail inclusion--long, curving feathery golden threads of byssolite or chrysotile--is unique to demantoid garnets from Russia. If it has that horsetail, there's no other source it can be from.
Tiny golden flecks of pyrite--like sparkling stars--are what visually set lapis lazuli apart from dark sodalite. These pyrite inclusions give the stone its unique and ancient beauty.
Moss agate--with dark green patterns suspended in translucent chalcedony--is only a milky stone without its inclusions. With them, it's like water in the forest, with bits of moss floating in a stream.
The simplest of inclusions--water--creates the magical appearance of this gem. Spheres of silica hold inclusions of water to create the play of color, trapping light inside and splitting wavelengths like a prism. What is an opal without the rainbow inside?
One of the most common and popular included gemstones is rutilated or tourmalinated quartz. The threads of gold (rutilated) or black (tourmalinated) in the clear quartz matrix are inclusions--yet they are sought out for their beauty. Rutiles can also appear in other gemstones, such as prehnite.
Ruby and Sapphire
The sister corundums, red ruby and the multiple colors of sapphire, are known to display asterism. Asterism will show a six- or twelve-rayed star moving across the surface of the stone; six-rayed stars are the more common form. These gems are frequently named (the Star of Asia, the Black Star of Queensland, the DeLong Star Ruby, etc.) and are in museums where they can be studied and appreciated. Asterism can also appear in rose quartz, garnet, spinel, chrysoberyl and diopside.
Tigereye, Tiger Iron and Others
Chatoyancy is an inclusion. That "cat's eye" effect in stones such as tigereye, tiger iron and cat's eye quartz is caused when a swath of rutiles line up in a stone. This grouping is called "silk" in the gemstone trade and creates the reflective shimmer that gives these stones their characteristic beauty.
While some gemstone buyers think that every inclusion is a flaw, gemologists know better. Inclusions, rather than lowering the value of certain gems, can be proof of natural origin, indicate source location, increase rarity and add value to an individual stone.
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