June Collective Collector's Corner
Natural Inclusions in Tourmaline: Growth Tubes, Fluids, Crystals & What They Mean
Tourmaline is celebrated for its extraordinary range of color, but its internal world can be just as fascinating. Growth tubes, fluid inclusions, mineral crystals, fissures and natural growth structures can preserve evidence of how a tourmaline formed while influencing clarity, brilliance, durability and value.
Few gemstone families offer the visual range of tourmaline.
Pink, red, green, blue, yellow, brown and multicolored crystals can all occur within the broader tourmaline group. Some crystals even develop dramatic color zoning, creating combinations such as pink and green watermelon tourmaline.
Tourmaline's internal world can be equally varied.
Under magnification, a natural tourmaline may contain long growth tubes, liquid filled cavities, tiny gas bubbles, mineral crystals, fine needles, healed fractures and intricate growth patterns.
Some are nearly invisible during normal viewing.
Others become obvious characteristics of the stone.
And in certain cases, inclusions create desirable optical phenomena rather than simply reducing clarity.
Inclusions are a natural and common part of tourmaline. The important question is not simply whether a stone contains inclusions, but how those features affect its beauty, transparency, durability and value.
Tourmaline also demonstrates why clarity expectations should never be applied identically to every color variety.
A fine pink or red tourmaline may remain highly desirable with visible natural features, while buyers generally expect considerably greater clarity from many green tourmalines.
This Collector's Corner guide explores those differences and the remarkable internal characteristics collectors may encounter inside natural tourmaline.
For the broader foundation first, explore the Natural Gemstone Inclusions Guide .
Why Tourmaline Can Contain So Many Inclusions
Tourmaline commonly develops in geological environments where mineral rich fluids are important to crystal formation.
As a tourmaline crystal grows, portions of those fluids can become trapped inside it.
Crystal growth can also be interrupted by other minerals or changing conditions, creating hollow or fluid filled tubes that record those growth interruptions.
Stress and geological activity may create fractures. Some fractures can later undergo natural healing, leaving fluid inclusions and intricate internal patterns behind.
The result is a gemstone that can preserve a remarkably complex record of its formation.
For collectors who enjoy microscopy, tourmaline can reveal miniature landscapes that are every bit as varied as its colors.
Are Inclusions Normal in Natural Tourmaline?
Yes.
Natural tourmaline frequently contains inclusions.
That does not mean every tourmaline should be heavily included, nor does it mean clarity is unimportant.
Instead, clarity has to be judged within the context of the particular tourmaline.
The color variety matters.
The intensity of the color matters.
The size of the gemstone matters.
The position and visibility of the inclusions matter.
And the intended use matters.
A vivid rubellite with exceptional red or pink color may remain desirable with eye visible natural inclusions.
A pale green tourmaline with the same degree of inclusion may be much less appealing because the features are easier to see and the color provides less visual competition.
This is one of the clearest examples of why colored gemstone quality is multidimensional.
Growth Tubes in Tourmaline
Growth tubes are among the most recognizable internal features found in tourmaline.
They can appear as long channels running through the crystal, often aligned with its growth direction.
Some are hollow.
Others contain fluid.
Some can terminate in tiny included crystals.
These tubes can form when a localized interruption prevents the tourmaline crystal from growing normally around a small object or area.
As crystal growth continues around the interruption, a channel remains behind.
Under magnification, these structures can appear remarkably straight and architectural.
They are part of the gemstone's natural growth record.
Collector's Perspective
A growth tube is not simply an empty line inside a gemstone. It can record a specific interruption in crystal growth and can sometimes contain fluids, mineral crystals or other microscopic material.
Growth Tubes and Cat's Eye Tourmaline
When numerous tube like inclusions are arranged in a parallel orientation, they can interact with light in a remarkable way.
If the rough is oriented and cut correctly as a cabochon, reflected light can form a bright band across the gemstone.
This phenomenon is called chatoyancy.
The resulting gemstone is known as cat's eye tourmaline.
In this situation, inclusions are not merely tolerated.
They create the optical phenomenon that gives the gemstone its distinctive appeal.
The quality of the cat's eye depends on factors including the concentration and orientation of the inclusions, transparency of the host material and quality of the cutting.
Tourmaline's cat's eye is often softer than the extremely sharp eye associated with fine cat's eye chrysoberyl, but beautiful examples can still be highly collectible.
Fluid Inclusions in Tourmaline
Fluid inclusions are another hallmark of tourmaline's internal world.
Tourmaline commonly forms in environments where fluids play an important role, and tiny portions of those fluids can become trapped during crystal growth.
Under magnification, these features may appear as threadlike cavities or irregularly shaped pockets.
Some contain liquid.
Some contain gas bubbles.
Others can contain multiple phases.
To a gemologist or collector, these inclusions can provide a tiny preserved glimpse into the conditions surrounding crystal formation.
To an ordinary jewelry buyer, their practical importance depends primarily on whether they are visible and whether they interfere with transparency, brilliance or structural integrity.
Threadlike Fluid Filled Cavities
Some of tourmaline's most characteristic inclusions appear as fine threadlike cavities running roughly parallel to the length of the original crystal.
Under magnification, liquid or gas bubbles can sometimes be observed within these structures.
Their visual effect varies greatly.
Fine isolated tubes can be nearly invisible without magnification.
Dense concentrations may reduce transparency.
Highly reflective internal features can also become more visually obvious as the gemstone moves through light.
As always, visibility and consequence matter more than the mere presence of the feature.
Mineral Crystal Inclusions
Tourmaline can also contain crystals of other minerals that became enclosed during growth.
Some appear as tiny transparent prisms.
Others may be dark, reflective or strongly colored.
A well formed included mineral crystal can be especially fascinating under magnification because the observer is essentially seeing one natural mineral preserved inside another.
Certain included crystals can interrupt the growth of the host tourmaline and produce growth tubes extending away from them.
That relationship can provide a vivid visual record of crystal development.
An included mineral can be gemologically interesting without being diagnostic of a particular geographic origin. Similar mineral inclusions can occur in tourmalines from more than one locality.
Fine Needles and Other Microscopic Features
Tourmaline may contain fine needle like inclusions in addition to more obvious growth tubes and fluid cavities.
These features may be difficult or impossible to see without magnification.
Their effect depends upon concentration and orientation.
A few fine needles may have essentially no influence on the face up appearance.
Dense or reflective needles may become much more visible.
For a collector, their arrangement and interaction with light can create another layer of interest within the stone.
Natural Fissures and Fractures in Tourmaline
Tourmaline can contain natural fissures and fracture related inclusions.
Some developed during or after crystal growth.
Others may show evidence of natural healing.
When a fracture partially heals, microscopic fluid inclusions or negative crystals can remain along the former fracture plane.
Under magnification, the feature can resemble a veil, feather, fingerprint or branching network.
The word fracture can sound alarming, but not every natural fracture presents the same practical concern.
A small healed feature deep inside the stone is different from a broad open fracture extending through a corner or girdle.
The individual feature must be evaluated.
Surface Reaching Inclusions in Tourmaline
Some natural tourmaline inclusions intersect the polished exterior.
These are surface reaching inclusions.
The term describes location rather than automatically diagnosing damage.
However, surface reaching features can affect polish and luster, and prominent open features may reduce desirability or require greater consideration before the gemstone is set.
The most useful questions are:
- How large is the feature?
- How deeply does it extend?
- Is it open at the surface?
- Is it visible when the gemstone is viewed normally?
- Does it interrupt the polish?
- Is it near a corner, point or thin girdle?
- Would a prong place pressure on it?
- Does it materially affect transparency or brilliance?
For the complete discussion, read Surface Reaching Inclusions in Natural Gemstones .
Color Zoning and Growth Structures
Tourmaline is famous for color zoning.
Different chemical conditions during crystal growth can create distinct color zones within a single crystal.
Some crystals change color along their length.
Others develop concentric zones from the center outward.
Watermelon tourmaline is perhaps the most familiar example, commonly displaying pink in the center surrounded by green material.
These zones are not conventional inclusions in the same sense as a trapped crystal or fluid cavity, but they are important natural growth features.
Color zoning can strongly influence cutting decisions.
A cutter may orient a tourmaline to showcase multiple colors deliberately or attempt to emphasize one dominant hue.
Clarity Expectations Vary by Tourmaline Color
One of the most important lessons in tourmaline buying is that clarity expectations change with color variety.
| Tourmaline Color or Variety | Typical Clarity Expectation | Buyer Perspective |
|---|---|---|
| Pink Tourmaline | Eye visible inclusions are commonly encountered. | Strong attractive color can outweigh moderate inclusion. |
| Red Tourmaline and Rubellite | Natural inclusions are frequently accepted. | Color is often the dominant value factor when inclusions are not overly distracting. |
| Green Tourmaline | Higher clarity is generally expected. | Obvious inclusions can have a greater negative impact on value. |
| Blue Tourmaline | Fine stones are generally preferred with good transparency. | Visible inclusions should be evaluated against rarity and color. |
| Multicolored Tourmaline | Expectations depend heavily on color pattern and presentation. | Exceptional zoning can become the primary attraction. |
| Cat's Eye Tourmaline | Oriented inclusions are required for the phenomenon. | The quality of the eye can outweigh conventional clarity considerations. |
Why Pink and Red Tourmaline Can Be More Included
Pink and red tourmalines frequently contain visible internal features.
The trade generally accepts more inclusion in these colors when the gemstone possesses strong attractive color.
This does not mean clarity is irrelevant.
A heavily fractured stone with low transparency will usually be less desirable than a cleaner stone of similar color.
But a vivid, beautifully saturated pink or red tourmaline can remain highly appealing with inclusions that would be considered less acceptable in a pale green tourmaline.
This is an important example of how value factors interact rather than operate independently.
Why Green Tourmaline Is Held to a Different Standard
Green tourmaline is generally expected to display greater transparency and fewer eye visible inclusions.
Because high clarity green material is available, buyers tend to be less tolerant of conspicuous inclusions.
A dark or central inclusion can therefore have a stronger effect on desirability.
Color still matters enormously.
A rich, lively green with strong transparency and good cutting can be exceptionally attractive.
But when two otherwise similar green tourmalines are compared, the cleaner stone will generally have the advantage.
How Color Can Hide or Reveal Inclusions
Color intensity changes the way inclusions are perceived.
An inclusion inside deeply saturated tourmaline may be difficult to notice.
The same feature inside pale material may be immediately obvious.
Light toned gemstones allow more of the internal scene to remain visible to the observer.
This means the visual effect of an inclusion depends partly on the gemstone surrounding it.
It also explains why macro photographs should be evaluated alongside normal face up photographs and video.
How Inclusions Affect Tourmaline Brilliance
A transparent faceted tourmaline relies on light traveling through the stone and returning through its facet structure.
A small isolated inclusion may have almost no effect on that process.
A large reflective fissure may interrupt it considerably.
Dense clouds or networks of inclusions can soften transparency.
Numerous reflective cavities may scatter light and create internal flashes.
Whether this effect is attractive or distracting depends on the individual gemstone.
The face up appearance should always remain the final visual test.
When Inclusions Affect Tourmaline Value
Inclusions generally reduce value when they noticeably interfere with beauty, transparency or durability.
Their impact depends on severity and context.
Consider two pink tourmalines.
One has exceptional saturated color, attractive cutting and a few visible natural fissures near the edge.
The other is cleaner but pale and visually flat.
The cleaner stone is not automatically the more desirable tourmaline.
Color often carries enormous weight.
Now compare two green tourmalines with similar color and cutting.
If one is highly transparent and the other contains obvious central inclusions, clarity may have a much stronger influence on the comparison.
This is why a universal clarity rule does not work well for tourmaline.
When Inclusions Can Add Value
Cat's eye tourmaline provides the clearest example.
Numerous aligned inclusions create the reflected eye.
Without them, the phenomenon would not exist.
The value of a cat's eye tourmaline can therefore increase when its inclusions produce a strong attractive optical effect.
Collectors may also value unusual inclusion scenes for their rarity and microscopic beauty.
A well formed mineral crystal inside transparent tourmaline can transform a gemstone into a miniature mineral specimen.
A dramatic growth tube can record crystal formation in a way that is visually fascinating.
These characteristics may have greater value to a collector than to a buyer seeking a conventionally clean jewelry stone.
Can Tourmaline Inclusions Prove Natural Origin?
Certain microscopic features can provide important identification evidence.
Growth tubes, fluid inclusions and natural mineral crystals can all contribute to a gemologist's interpretation.
But the mere presence of an inclusion should not automatically be treated as proof that a gemstone is natural.
Synthetic materials can contain their own characteristic inclusion scenes.
Treatments can alter natural features.
And not every natural tourmaline displays obvious diagnostic inclusions.
Professional identification considers multiple observations and test results together.
Inclusions are evidence, not a universal shortcut to gemstone identification.
Can Inclusions Reveal Tourmaline Geographic Origin?
Some mineral inclusions and microscopic scenes can be associated with particular geological environments.
However, many inclusion types occur across multiple tourmaline deposits.
A particular included crystal therefore may be interesting without being diagnostic of geographic origin.
Professional origin work can require chemistry, spectroscopy and comparison with established reference samples.
Collectors should be cautious about assigning a locality from a single visible inclusion.
Tourmaline Inclusions and Durability
Tourmaline is appropriate for many jewelry applications, but significant fractures deserve individual evaluation.
A small internal tube is not the same durability concern as a broad open fissure.
Location matters.
Features near the girdle, corners or points may deserve particular attention.
Setting pressure matters as well.
A meaningful fracture positioned exactly beneath a prong should be discussed with the jeweler before the stone is mounted.
Good jewelry design works with the internal architecture of the gemstone rather than treating every stone identically.
Tourmaline Inclusions and Jewelry Settings
Protected Rings
Tourmalines selected for rings can benefit from settings that protect exposed edges and corners, particularly when meaningful natural features are present.
Pendants
A pendant generally experiences less impact than a ring and may be an excellent choice for beautiful tourmalines that deserve more thoughtful wear.
Earrings
Earrings are another relatively protected application and can showcase color without exposing the stone to the same mechanical environment as a ring.
Custom Design
A custom jeweler can position prongs and protective elements around the individual architecture of the gemstone.
How Cutters Work With Tourmaline Inclusions
Tourmaline crystals commonly form as elongated prisms.
Cutters have to consider both color orientation and internal features when deciding how to fashion the rough.
A growth tube may influence orientation.
A significant fissure may determine where material must be removed.
Color zoning may encourage a cutter to preserve a particular section of the crystal.
Included material with exceptional color may be fashioned as a cabochon rather than a transparent faceted stone.
Material containing aligned tubes may be specifically oriented to produce a cat's eye.
Cutting is therefore an exercise in interpreting the entire crystal rather than simply imposing a predetermined shape.
Why Macro Photography Can Make Tourmaline Look More Included
Macro photography is valuable because it reveals details buyers could never see in an ordinary photograph.
It can also create a misleading sense of scale when viewed without context.
A tourmaline only several millimeters across can fill an entire phone screen.
A tiny fluid inclusion then appears enormous.
A narrow surface opening may look like a major fracture.
The photograph can be technically accurate while still presenting the feature at a scale far beyond normal viewing.
When buying online, compare magnified images with normal face up photographs, video and the actual measurements of the stone.
Eye Clean Does Not Mean Inclusion Free
A tourmaline described as eye clean can still contain numerous microscopic inclusions.
Eye clean generally means that inclusions are not readily visible without magnification under normal viewing conditions.
It does not mean the crystal formed without inclusions.
This distinction is especially important when looking at highly magnified listing photographs.
A gemstone can appear beautifully clean during normal use while showing an intricate internal landscape under a loupe or microscope.
What Should Buyers Look for in an Included Tourmaline?
Evaluate the Complete Stone
- Look at the tourmaline face up before using magnification.
- Evaluate hue, tone and saturation.
- Consider whether the clarity is appropriate for that tourmaline color.
- Check whether inclusions are visible without magnification.
- Determine whether they reduce transparency or brilliance.
- Look for significant fissures near the girdle, corners or points.
- Ask whether any inclusion reaches the surface.
- Evaluate whether surface reaching features interrupt the polish.
- Consider the intended jewelry setting.
- Compare macro photographs with normal viewing photographs.
- Ask whether any treatment has been disclosed.
- Consider rarity and color before judging clarity in isolation.
- Evaluate whether the price reflects the complete gemstone.
When Should You Pass on an Included Tourmaline?
A tourmaline may deserve a pass when its inclusions materially undermine the qualities you are purchasing it for.
A transparent faceted gemstone that appears dull because of dense internal fracturing may not offer the light performance you want.
A large open fissure extending through a vulnerable corner may create an unnecessary durability concern for an everyday ring.
A strongly visible central inclusion may be too distracting at the asking price.
A pale green tourmaline with obvious inclusions may have difficulty competing with cleaner material readily available in the market.
The issue is consequence.
Not simply presence.
When an Included Tourmaline Can Be an Excellent Choice
An included tourmaline can be extremely desirable when the total gemstone is compelling.
Exceptional color can dominate the visual experience.
An inclusion near the edge may disappear during normal viewing.
A surface feature may have little practical significance in a protected pendant.
An unusual internal crystal may make the gemstone more fascinating to a collector.
Aligned inclusions may create chatoyancy.
The correct question remains:
What does this inclusion actually do to this gemstone?
Collector Appeal: Tourmaline as an Internal Landscape
Tourmaline rewards magnification.
A gemstone admired for color from across the room can become an entirely different object under a microscope.
A growth tube records interrupted crystal development.
A fluid inclusion preserves material associated with the environment in which the crystal formed.
An included mineral becomes a specimen inside another specimen.
A healed fracture records geological disruption and recovery.
Color zoning documents changes in chemistry as the crystal developed.
For collectors, these are not merely flaws.
They can be part of what makes one natural tourmaline impossible to duplicate.
Frequently Asked Questions
Are inclusions common in natural tourmaline?
Yes. Tourmalines commonly contain fluid inclusions, growth tubes, crystals, needles and fracture related features. The expected degree of clarity varies by color and variety.
What are growth tubes in tourmaline?
Growth tubes are elongated hollow or fluid filled channels produced by localized interruptions during crystal growth. They often follow the original crystal's growth direction.
Why does tourmaline contain fluid inclusions?
Tourmaline commonly forms in fluid rich geological environments. Small portions of those fluids can become trapped within the growing crystal.
Can inclusions create a cat's eye in tourmaline?
Yes. Numerous parallel tube like inclusions can reflect light as a band when the rough is correctly oriented and fashioned as a cabochon, producing chatoyancy.
Are pink tourmalines normally included?
Pink and red tourmalines commonly contain visible inclusions, and buyers generally tolerate more inclusion in these colors when the color is strong and attractive.
Should green tourmaline be eye clean?
Higher clarity is generally expected in green tourmaline. Eye visible inclusions can have a greater negative influence on value than they might in fine pink or red material.
Does a surface reaching inclusion mean tourmaline is damaged?
No. A natural internal feature can intersect the polished exterior. The feature should be evaluated for size, location, openness and durability rather than judged solely by the phrase surface reaching.
Do inclusions prove a tourmaline is natural?
Not by themselves. Certain inclusion scenes can provide important identification evidence, but professional gemstone identification considers multiple observations and test results.
Can tourmaline inclusions determine geographic origin?
Some features may provide supporting evidence, but many inclusions occur in tourmalines from multiple localities. Geographic origin should not generally be assigned from one inclusion alone.
Should I avoid included tourmaline?
Not automatically. Evaluate color, transparency, brilliance, inclusion location, durability, rarity, intended use and price together. A beautifully colored included tourmaline can be a far more appealing gemstone than a clean stone with weak color.
The June Collective Perspective
Tourmaline is one of nature's most expressive gemstone families.
Its colors can move from soft blush pink to saturated red, forest green, electric blue and extraordinary combinations within a single crystal.
Its inclusions can be just as varied.
Growth tubes record interrupted crystal development.
Fluid inclusions preserve traces of the environment in which the crystal grew.
Mineral crystals become miniature specimens inside the gemstone.
Natural fissures can record geological stress and healing.
And aligned inclusions can create the reflected eye of chatoyant tourmaline.
The goal is not to pretend every inclusion is desirable.
Some reduce transparency.
Some affect polish.
Some reduce value.
Some require consideration before setting.
But the presence of an inclusion should begin an evaluation rather than end it.
Look at the color.
Look at the transparency.
Look at the location of the feature.
Consider the particular tourmaline variety.
Consider how the stone will be worn.
Then evaluate the complete gemstone.
At June Collective, gemstones are evaluated in our small in office gemological workspace using standard gemological tools and observation to help us describe the stones we offer accurately and transparently.
When definitive identification, treatment determination, geographic origin or other advanced analysis materially affects a gemstone's value, an independent gemological laboratory remains the appropriate authority.
The more buyers understand natural gemstone characteristics, the more confidently they can appreciate the individuality that makes tourmaline so extraordinary.
Continue Exploring June Collective
Build your foundation with:
Natural Gemstone Inclusions Guide
Surface Reaching Inclusions in Natural Gemstones
Continue through Collector's Corner:
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