Types of Inclusions in Natural Sapphire, Emerald, and Ruby

An image displaying hydrocarbon and petroleum inclusions in Quartz

Image credit- Icminerals

Anyone who has ever bought a piece of gemstone jewelry or been interested in the world of minerals would probably know that inclusions play an instrumental role in grading or evaluating a gemstone’s quality, overall visibility, and shine.

Most of you will remember the infamous "Mosquito fossil trapped in a yellow amber scepter" carried by John Hammond in the movie Jurassic Park. Look at the image below!

• Image credit- Jurassic Park Fandom

Although Hammond had a different motive to extract amber from mines, he was still able to give the world one of the best examples of one of many inclusions found in precious and semi-precious gemstones.

WHY ARE INCLUSIONS IMPORTANT?

Geologically, inclusions are foreign matter, materials, or cavities trapped inside gemstones during their natural formation. According to mineralogist James Hutton, some of the inclusions enclosed may even be older than the host rock itself. These inclusions may exist in various forms: solid, liquid, or gaseous.

Many gemstones contain microscopic irregularities that may not be visible to the naked eye, while others can be directly identified upon close inspection. Inclusions can reveal so much about a gemstone, including its geological growth, age, treatment process, chemical composition, features, value, etc.

All in all, inclusions help gemologists determine the exact value of a colored stone. In some cases, distinctive inclusions enhance the beauty and features of a gemstone, such as blue sapphires and opal.

In this article, we are taking a look at various inclusions found in Natural Sapphire, Ruby, and Emerald.

INCLUSIONS IN NATURAL SAPPHIRE

Sapphires, found in igneous or metamorphic geological environments, may host a variety of inclusions. Even the so-called "eye-clean" sapphires may contain some type of inclusion. In fact, the best clarity-graded sapphire with no inclusions at all is often viewed with suspicion.

Types of inclusions found in natural sapphires:

An image displaying types of inclusions and other growth features found in natural sapphire

Image credit- Sapphire rings

1. Silk: It is one of the most famous inclusions found in sapphires. These tiny, rutile needle-like irregularities are what give some sapphires their dreamy transparency. They frequently go by the name "needles," since they typically appear in bunches and resemble dark crossband stone patterns. Star sapphires' asterism is also a result of silk. One element that might truly increase the value of sapphire to a magnanimous level is silk. When present in a cut sapphire in a reasonable proportion, the highly reflective rutile needles scatter light perfectly illuminating the gemstone's deeper facets and elevating its bright appearance.

2. Color Zoning: In a gemstone, these are regions or bands of contrasting color. Color zoning is extremely typical in the raw form and happens frequently during the crystallization process, which occurs naturally. This kind of inclusion can be significantly reduced or enhanced by cutting the sapphire.

3. Fingerprint Inclusion: These are collections of teeny, liquid-filled tubes arranged in networks that mimic fingerprints. When sapphires re-crystallize to partially mend a fracture zone, fingerprint inclusions are created. Although these kinds of inclusions are very typical in sapphires, their modest size means that they are unlikely to have a negative effect on the sapphire's quality.

4. Fractures: These are those inclusions that are oblong or round and surround solid or liquid patterns. These fractures are the result of stress brought on either by the radioactive disintegration of minute zircon crystals or by the intense heat needed for heat treatment.

5. Cavities: These are empty spaces or holes that penetrate a gemstone's interior from the surface. A standard procedure called "cavity filling" is applied to fill the cavities. It usually includes introducing color-infused glass in the gem structure ultimately resulting in an improved appearance of inclusions.

6. Feathers: These are tiny imperfections that resemble feathers in their appearance. These are normally white in color; if they are large enough, they may compromise the stone's structural stability. Minute feather inclusions may not typically affect the stone’s overall appearance.

7. Liquid Inclusions: These are cavities within a gemstone that are liquid-filled. The existence of carbon dioxide fluid inclusions in the corundum of metamorphic origin is really a sign that no heat treatment has been performed to change the stone.

INCLUSIONS IN RUBY

Ruby contain nine types of inclusions, including needles, cavities, and feathers, which are typically similar to sapphires. However, they also contain some types of inclusions like crystals and scratches that are specific to rubies. Let’s take a closer look at each:

Types of inclusions found in Rubies:

A visual representation of types of inclusions found in rubies.

Image credit- GIA

1. Cavities: These represent the empty spaces that extend to the gemstone’s surface. Cavity-filling is a standard procedure used to fill these fractures with color-infused glass. However, extreme cavities may be difficult to fix, leading to durability issues in the long run. When this occurs, the stone is heated with flux to improve color and restore durability.

2. Color Zoning: Color zoning, which is a concentration of color in various regions of a stone, is typical of all corundum variations. Color zoning can occasionally be used by cutters to provide color to areas of the stone that lack it.

3. Fingerprint Inclusion: Inclusions resembling human fingerprints are extremely common in rubies. These imperfections are often tiny and hardly ever affect a ruby's quality.

4. Liquid Inclusion: These are cavities within a gemstone that are liquid-filled. The existence of carbon dioxide fluid inclusions in the corundum of metamorphic origin is really a sign that no heat treatment has been performed to change the stone.

5. Silk Inclusion: Inclusions made to resemble silk fibers are common in rubies. These flaws can change how the light reflects through these gemstones, but they normally have little effect on the color and clarity of a ruby.

6. Needle Inclusion: The term "needle" refers to a significantly longer and skinnier version of a crystal inclusion seen in rubies. Though any kind of crystal can be used to create them, some are more common in corundum than others. Needles can also be considered to be hollow tubes inside the gemstone.

7. Scratches: Scratches are surface-level imperfections that are often removable with polishing. The stone's carat weight will drastically fall if the damage is deep, necessitating additional polishing.

INCLUSIONS IN EMERALD:

Emeralds are Type III gemstones, a type that typically shows signs of inclusions. Inclusions in green emerald stone are often described as "Jardin" french for the garden because these inclusions resemble the moss or plants found in gardens. Emeralds with inclusions are very sensitive and thus require great care.

Types of inclusions found in Emeralds:

An image displaying photomicrographic inclusions and other growth features found in emeralds

Image Credit- Emeralds.com/GIA

1. Liquid Inclusions: Liquid inclusions filling emerald holes are quite typical. A gas bubble and a two-phase inclusion can also occur in those voids. A three-phase inclusion, where a gas, liquid, and crystal formation occur, is particularly prevalent in emeralds. In extremely unusual circumstances, the cavity's gas bubble or embedded crystal may shift.

2. Color Zoning: Color zoning is a term used to describe varied concentrations of coloration found in emeralds, although it is less typical in emeralds than it is in other gems like sapphires or tourmalines. For example, if one side is green while the other is missing a color.

3. Fingerprint Inclusion: Although more common in rubies or sapphires, fingerprints can also appear in emeralds. They can appear thicker and coarser, yet frequently resemble Though they can also resemble wispy veils, they frequently resemble the fingerprints we use to identify ourselves. They come in a variety of looks, which is true with most things. Fingerprints are examples of two-phase inclusions since they can develop with liquid and gas inside of them.

4. Fractures: Unlike cracks which many people may confuse for fracture, are common in emeralds. Most of the world’s emeralds are oiled and treated with resins to enhance their clarity and improve the flaws caused by fractures.

5. Crystal Inclusion: The presence of crystals of other minerals found inside the structure of emeralds is categorized as one irregularity. It is possible that another mineral surrounding the emerald may have gotten trapped during the formation of the emerald.

6. Needle Inclusion: The presence of thin crystals present in the emerald’s structure.

CONCLUSION

In mineralogy, inclusions are an interesting area of study for gemologists and are helpful in recognizing the properties of a gemstone more accurately than other methods. In many cases, they can accurately indicate a gemstone’s origin, features, chemical composition, the environment in which it was formed, etc. But inclusions can exist in various forms. In this blog, we took a look at the types of various inclusions found in natural sapphires, rubies, and emeralds to help our readers understand the best way to know whether they are buying a genuine gemstone or not.

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