Introduction to Faceting Mini Course
Inclusions and Cutting Strategy
Imagine holding a rough emerald worth thousands of dollars. Inside, you spot a dark crystal inclusion right in the center. Do you cut it out and lose 40% of the stone's weight? Or do you leave it in and risk creating a less valuable gem? This decision separates amateur cutters from master faceters.
Every gemstone tells a story through its inclusions—those tiny foreign materials trapped inside during formation. For faceters, these inclusions present both challenges and opportunities. Understanding how to work with them can mean the difference between creating a masterpiece and producing a mediocre stone.
What You'll Learn:
- How to evaluate inclusions and make smart cutting decisions
- When removing inclusions helps versus hurts gem value
- How different jewelry settings affect inclusion visibility
- Techniques for managing various types of inclusions
- Why some inclusions should stay while others must go
Understanding Gemstone Inclusions
What Are Inclusions?
Inclusions are any materials trapped inside gemstones during their formation. These can be solid crystals, liquid-filled cavities, gas bubbles, or internal fractures. Think of them as nature's fingerprints—each inclusion tells part of the gem's geological story.
Not all inclusions are bad. Some actually add value to gemstones. Rutile needles in quartz create spectacular "golden hair" effects. Star sapphires owe their beauty to silk inclusions that create chatoyancy. Even some emerald collectors prefer stones with their characteristic "jardin" (garden) of inclusions.
Types of Inclusions Faceters Encounter
Solid Inclusions are the most common type. These include crystal inclusions, where one mineral grows inside another. A ruby crystal inside another ruby is nearly invisible due to matching refractive indices. However, a dark spinel crystal in a light sapphire stands out dramatically.
Fractures represent weak points in gems. Unlike other inclusions, fractures almost always need removal. They create structural weaknesses that can lead to breakage during setting or wear. Only in very rare cases—when fractures are tiny, internal, and in tough gems—should you consider leaving them.
Veils are partially healed fractures that look like wispy fingerprints. These allow some light to pass through, making them less problematic than solid inclusions. Small veils often disappear in a gem's reflections and may not be worth removing.
Balancing Aesthetics and Weight Retention
The Value Equation
Every inclusion management decision comes down to a simple question: Will the gem be more valuable with the inclusion removed or left in place? This calculation involves two key factors—the visual impact of the inclusion and the weight loss from removal.
Consider a 5-carat sapphire with a small inclusion near the edge. Removing it might reduce the stone to 4.2 carats but create a clean gem. If clean 4.2-carat sapphires sell for $3,000 per carat while included 5-carat stones bring $2,000 per carat, the math is clear: $12,600 versus $10,000 favors removal.
However, the calculation isn't always straightforward. Sometimes removing a small inclusion requires cutting away much more material to maintain proper proportions and symmetry.
When to Keep Inclusions
Size Matters More Than You Think. Many inclusions visible under magnification disappear to the naked eye. Before making any cutting decisions, examine your rough without magnification. You'll be surprised how many "problems" vanish when viewed normally.
Location Is Everything. The worst place for an inclusion is directly under the table, especially in the culet area of brilliant cuts. Diamond cutters call this a "stab in the heart" because reflections multiply the inclusion's appearance. Conversely, inclusions under crown facets near the girdle have minimal visibility.
Relief Considerations. Dark-colored gems like garnets naturally hide inclusions. Most red garnets contain black inclusions that are visible close up but disappear from normal viewing distances. Since garnets are cut more for color than brilliance, these inclusions rarely impact value significantly.
Strategic Cutting Approaches
Orientation Changes can solve many inclusion problems without material loss. Sometimes simply cutting the stone from a different direction moves the inclusion to a less visible location or eliminates it entirely.
Partial Removal works for small inclusions. Instead of cutting them out completely, position them at the stone's edge. This technique requires skill but can save significant weight.
The 16 Main Round Advantage. This cutting style creates curved crown facets that offer better views of the gem's interior. While this makes the stone appear larger and cleaner, it also makes inclusions more visible. Never try to hide inclusions under these crown facets—you'll make them stand out instead.
Open vs. Closed Settings and Impact on Visibility
Understanding Setting Types
Jewelry settings dramatically affect how inclusions appear in finished pieces. The choice between open and closed settings can make inclusions more or less noticeable, impacting both beauty and value.
Open Settings expose the pavilion (bottom) of gemstones, allowing light to enter from multiple directions. Prong settings, tension settings, and basket settings are common examples. These maximize brilliance but also make inclusions more visible by illuminating them from various angles.
Closed Settings have solid metal backs that block light from entering the pavilion. Bezel settings and some vintage mounting styles use this approach. While they may reduce brilliance slightly, they can effectively hide inclusions in the lower portion of gems.
Light Behavior and Inclusion Visibility
Light entering through an open setting can transform minor inclusions into major visual distractions. Veils that seemed insignificant in rough can become prominent when backlit. Conversely, small crystal inclusions near the pavilion might disappear entirely in closed settings.
This phenomenon particularly affects emeralds and other Type III gems (heavily included stones). Many antique emerald pieces use closed settings specifically to minimize inclusion visibility while maximizing color intensity.
Cutting Strategy Based on Setting Choice
For Open Settings, focus on removing inclusions that will be backlit. Pavilion inclusions become much more noticeable in open settings. However, crown inclusions may remain acceptable since they're not as strongly illuminated from behind.
For Closed Settings, you can be more lenient with pavilion inclusions while being stricter about crown inclusions. Since light primarily enters from the top, crown inclusions become the main visibility concern.
Pre-Planning Benefits. When possible, know the intended setting before cutting. This knowledge allows you to optimize inclusion management for the specific mounting style, potentially saving valuable material.
Advanced Inclusion Management Techniques
Working with Fractures
Fractures require special attention because they represent structural weaknesses. If a fracture extends to the surface, it must be removed—no exceptions. Internal fractures should also be eliminated unless they meet very specific criteria: tiny size, complete internal containment, and location in a tough gem with no cleavage.
Removal Techniques vary by fracture location. Edge fractures can be ground away on cabbing wheels or coarse laps. Internal fractures require sawing the rough into multiple pieces along the fracture line.
Veil Management Strategies
Veils offer more flexibility than solid inclusions. Fine, transparent veils often disappear in finished gems and don't justify the weight loss from removal. However, their visibility depends heavily on orientation and location.
Vertical veils running from culet to crown are less visible than horizontal ones crossing the girdle plane. Consider the veil's position relative to the stone's center—off-center veils in the crown area may be acceptable, while centered ones typically need removal.
Creative Solutions
Carving Techniques can sometimes camouflage inclusions without significant weight loss. Small surface-reaching inclusions might be incorporated into decorative elements or carefully carved away.
Specialty Cuts like the 16 Main Round can either enhance or hide inclusions depending on placement. The curved crown facets create a "fountain of light" effect that can make clean areas appear larger while potentially highlighting problem areas.
Economic Considerations
Professional vs. Hobbyist Approaches
Professional faceters must consider labor costs when managing inclusions. Sometimes accepting a slightly included stone is more profitable than spending hours removing minor inclusions that barely affect value.
Hobbyists have more flexibility to pursue perfection, but should still consider whether the effort matches their satisfaction with the result. Cutting heavily included material can provide valuable learning experiences about inclusion management.
Market Factors
Different gem markets have varying tolerance for inclusions. Commercial jewelry often accepts inclusions that collectors would reject. Understanding your target market helps guide inclusion management decisions.
High-value material like fine emeralds or Kashmir sapphires justifies more careful inclusion management, while commercial-grade material may be cut primarily for yield.
Summary
Inclusion management represents one of faceting's greatest challenges, requiring both technical skill and business acumen. Success comes from understanding how inclusions interact with light, how settings affect visibility, and how to balance aesthetics with practical considerations.
Key Takeaways:
- Always examine inclusions without magnification before making removal decisions
- Consider the intended setting when planning inclusion management
- Location matters more than size for inclusion visibility
- Fractures almost always require removal, while veils offer more flexibility
- The 16 Main Round cut enhances interior visibility—use carefully with included stones
- Economic factors should guide professional cutting decisions
- Practice with various included materials builds essential judgment skills
Mastering inclusion management takes time and experience. Every stone presents unique challenges, and even expert faceters sometimes make mistakes. The key is learning from each decision and gradually developing the judgment to balance all factors effectively. With practice, what seems like an impossible choice today becomes an obvious decision tomorrow.
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