Emerald is among the most popular stones worldwide, especially for May babies. Did you know that top-quality emeralds can be worth more than diamonds on a per-carat basis? There are many reasons why emeralds can be your favorite stone, even if you weren’t born in May. In this article, we will discuss something that makes them unique -emerald inclusions.
Where Is Emerald Found?
Emerald, the beryl family’s distinct green member, is found worldwide in three different types of rocks – igneous, metamorphic, and sedimentary.
Emerald is rare because beryllium, a necessary ingredient, is an element that occurs in very small amounts in the earth’s crust. You can’t bake an emerald cake without all the right ingredients.
How Does Emerald Get Its Color?
Owing its color to trace amounts of chromium, vanadium, and iron, most emerald today comes from Colombia, Zambia, Brazil, and Zimbabwe.
Observing inclusions in colored gemstones can be essential in determining a gem’s identification, quality, and origin. This is especially true of emeralds.
Under low magnification, most emeralds are said to have a garden of inclusions called a “jardin.” Here are some things you can find in a natural emerald jardin.
Three-phase Emerald Inclusions
Let’s start with three-phase emerald inclusions. Until recently, the observation of three-phase inclusions in emerald was considered an indicator of Colombian origin.
However, a recent study by the GIA discovered that emeralds from Afghanistan, China, and Zambia might also contain three-phase inclusions resembling those often found in Colombian specimens. These three-phase inclusions are jagged and contain a liquid, a gas, and a solid – the three phases of matter.
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Three-phase inclusions are normally formed when homogeneous fluid trapped in a cavity separates into three phases during the cooling process.
Colombian emeralds, specifically, are said to be the purest emeralds in the world because Colombian emerald deposits are the only ones on earth found in the sedimentary host rock rather than igneous rock.
The tectonic movements that created the Andes Mountains forced the raw elements of emeralds into liquid and gaseous states.
Parasite Emerald Inclusions
Another unique Colombian emerald inclusion is called a “parasite.” It’s a group of fluoro carbonate minerals. All members of this group are very rare, but the parasite is the most common.
On its own, parasite as a gem is typically brownish-yellow in color and has a hardness of four and a half on the Mohs scale. It lacks brilliance and has low dispersion, and it’s mildly radioactive but perfectly safe.
Mostly, these stones are of interest to collectors of rare minerals. If you find one in an emerald, that’s a double whammy. The GIA reported these parasitic crystals as inclusions to be found only in hydrothermal deposits of emeralds from the Colombian Musso mines.
Trapeze Emerald Inclusions
Probably the most unique emerald inclusion is found with the Colombian “trapeze” emerald. These patterned gems were first discovered by emerald miners and named “trapeze” – the Spanish word for cogwheel. A cogwheel at the time was a wheel with interlocking teeth used to grind cane sugar.
Trapeze emeralds are mined in the eastern Cordillera Basin of Colombia, where the host rock consists of black shale. The uniquely patterned gems consist of a central core of six rays or arms.
Black shale dendrites are a variety of shale that contains abundant organic matter. The shale is crystalline and has a tree-like structure that forms between the arms and the core due to fluid pressure exceeding normal atmospheric values. This is followed by a sharp decompression that causes rapid crystallization.
During this process, the particles of the black shale get trapped between the growth zones of the emerald crystals.
Did you know you can also find trapeze, ruby, sapphires, tourmaline, muscovite, and emeralds?
Amphiboles-splintering Emerald inclusions
They occur as thin needle-like or splintering inclusions.
For example, emeralds from the Ural Mountains contain blades of green actinolite fibers which look like bamboo. Austrian emeralds from Hobocto have green actinolite or granite fibers, and Zimbabwean emeralds from the Sandawana mine contain green curved tremolite fibers.
Other mineral inclusions, including pyrite, calcite, and mica flakes, can occur across all emeralds. There are also rarer inclusions, like purple fluorite and thin film fluid inclusions in emeralds from Russia.
Man-made Emerald Inclusions
Everything we’ve covered so far applies to natural stones, but did you know that man-made emeralds can also have their own unique inclusions? They’re a great way to tell the two apart.
Under the microscope, synthetic emeralds, especially hydrothermal ones, have some pretty cool inclusions. They will have spiky inclusions that look like nail heads. One of the most identifiable inclusions in hydrothermal synthetic emeralds are the chevron-like growth patterns or a roiling effect. You may also see healed whitish feather-like or branch-like conclusions in the Gilson emerald.
As far as treated stones go, many commercial emeralds are treated with oil or polymer resins. These are injected into the stone filling internal fractures. This can hide fractures and temporarily enhance the appearance, improving color and clarity. Even with a microscope, detection of this treatment can be challenging.
High magnification may reveal interference colors in the fractures. Sometimes the oil doesn’t fill in all the way, and you can see gaps. Conversely, a well-filled fracture may display a diagnostic blue flash, confirming its clarity enhancement. Most of the emeralds sold in crystal shops are treated in some way, and there’s nothing wrong with that as long as it’s properly disclosed.
This post on emerald inclusions sheds light on the intricate and fascinating world of gemology. It highlights the importance of studying and understanding the unique features of emeralds and how they can reveal valuable insights into the geological processes. The post also emphasizes the significance of emerald inclusions in determining the quality and value of these gemstones.