What Are Inclusions?

A photo of a Lithium Quartz Cluster

 

People who ask ‘What are inclusions’ typically fall into one of two categories — the gem collector or the diamond shopper.

Since we focus on gem and mineral collecting here at fox&toad, we’ll tackle more of that side of the answer. That said, inclusions are the same — whether in an amethyst or a diamond — so you should find your answer regardless.

The only way the answers differ is if you’re referring to value. While certain inclusions can make a collectable gem or mineral substantially more valuable, visible inclusions can drastically decrease the value of a gemstone grade diamond.

In other words — mineralogy tends to  like inclusions, gemology typically does not.

What Are Inclusions?

In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation. In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior.

Inclusions can be just about anything — from fluid to solids — including other gemstones, minerals or organic or inorganic material.

Inclusions can show in one specific clarity zone in a specimen or spread throughout, even changing the color or appearance of the stone.

This is especially true with some quartz inclusions. Chlorite for example, can give an entire clear quartz specimen a green color (see photo for example), whereas a fluid inclusion can appear as a tiny black dot or as a large bubble that moves as you move the specimen.

Lithium Quartz (pictured at the top of this page) contains varying amounts of lithium that can change the color of the entire quartz specimen to a pink or peach color.

Research has shown that the included material trapped inside mineral inclusions is typically older than the mineral itself. 

What are the Different Types of Inclusions?

There are many different types of inclusions, so we will stick to the most common and the ones we are most asked about.

Keep in mind that many inclusions may appear as one thing, but be something totally different. This is very common in fluid inclusions. The only way to truly know what is included in a gem or mineral is to break the specimen open and test it.
For obvious reasons, we never advise anyone to take this step.

    • Fluid inclusions: This is a term that often divides mineral and gem collectors. In recent years, the term “Enhydro” has become the common name for a stone that has fluid, or a bubble, inside of it.

      Scientifically, this is not the proper term to use, as Enhydro means “with water.” Without testing that material inside, there is no way to know for certain if the fluid you see is water or another liquid. That’s why many refer to them as fluid inclusions, which covers all liquids.

      That said, the term has become commonly accepted and used. Fluid inclusions can be static, meaning that they’re a small non-moving bubble, or they can form within an inner cavity in a crystal and move as you move the specimen.

      Keep in mind that some types of fluids can change when conditions change. Never keep a fluid included specimen in an area where it can freeze or get very warm — as it can destroy the bubble inside.

      As such, you shouldn’t rapidly shade a fluid inclusion, as you could potentially rupture the bubble and break it into multiple smaller bubbles that are harder to view.
  • Petroleum inclusions: Much like fluid inclusions, petroleum inclusions can happen if oil or another petroleum-based substance becomes trapped in a stone. These are especially common in Herkimer Diamonds that have a golden look.

    Petroleum inclusions can appear clear, but typically show in a golden color that can exist in one zone of a specimen or throughout the entire crystal.

    This can also happen when gas vesicles become trapped inside of a host crystal and appear as inclusion bodies within the stone.
  • Carbon Inclusions: Coal and graphite are common carbon inclusions and can appear as black rods or as solid black masses within a crystal.
  • Other Solid Inclusions: You can sometimes find included material that features other minerals (tourmaline, copper, silver, gold) or even organic inclusions, such as bugs trapped inside million-year-old amber.

  • Inclusions are an amazing window into a world long ago abandoned in pursuit of “progress.” Fluid trapped inside of a host crystal may have been there for hundreds of thousands of years — or longer.

    Insects or other animals trapped inside amber may be extinct or endangered — which provides the only view we have today of these species.

    And keep in mind that you might not see all visible inclusions with the naked eye. A gemologist uses 10X magnification or a jeweler’s loupe to view even the slightest inclusion and organelles that you otherwise may never notice.

    What Minerals Can Have an Inclusion?

    Since a crystal inclusion forms in nature, with many other organic and inorganic materials regularly coming into contact with it, there’s no limit as to what minerals or crystals can have inclusions.

    The most common included crystal offered to collectors is quartz. That’s because most quartz provides a clear window to view the suspended inclusion inside. 

    This can include a diamond, clear quartz, Herkimer Diamond, Smoky Quartz, Citrine or other quartz specimen.

    Among the Amethyst family of gemstones, the Super Seven Amethyst is an especially valuable and sought-after piece because of its metaphysical properties. These stones get their name from the seven inclusions they contain: Amethyst, Clear Quartz, Smoky Quartz, Cacoxenite, Goethite, Lepidocrocite and Rutile Quartz.

    Amber is another material often associated with inclusions — as the film Jurassic Park made insect-included amber a craze among collectors and non-collectors alike. 

    Some Ethiopian Welo Opals have ghosted inclusions that resemble an egg inside of the host opal.

    Clear Quartz can feature tourmaline inclusions (also known as tourmalination). These include Tourmalinated Quartz (with Black Tourmaline) or Indicolite Included Quartz (with Blue Tourmaline).

    A host crystal can even include a microscopic granule of dirt or sand that qualifies as an inclusion.

    Sapphire is prone to inclusions of hematite, zircon, spinel, calcite and mica.

    Organic — and sometimes living — gemstone inclusions can cause fluorescence or phosphorescence within a material.

    And not all inclusions are isolated inside of a host mineral or crystal. External inclusions can happen when a material trapped inside penetrates through the crystal and continues to grow outside of the stone. 

    This can create an internal inclusion and external inclusion.

    Colored gemstones sometimes have a harder time showing inclusions, as they color can mask the appearance of internal material. Clear Quartz, on the other hand, is a perfect frame for a showy inclusion.

    Are Inclusions Bad?

    This depends upon who you are talking to. If you’re purchasing (or selling) a jewelry-grade gemstone, such as a diamond or sapphire, an inclusion can greatly diminish the stone’s value or the diamond clarity grade.

    A flawless diamond, for example, is the most valuable type of specimen and has no internal inclusions or flaws on the diamond’s surface. It’s internally flawless and externally perfect and has unmatched clarity.

    A small diamond inclusion can lower the value of a stone by many thousands of dollars. GIA Certified Diamonds come with a certificate that details any inclusions found within a stone.

    On the other hand, a gem or mineral collector might pay a substantial premium for a specimen with a visible liquid inclusion or a solid inclusion.

    Inclusions give a host stone character and provide a window into the world in which it grew. If you’re looking for a gem or mineral to add to your collection that will provide years of viewing pleasure, you can’t go wrong with inclusions.