Understand best practices, bench risks, setting standards, and customer care when working with soft and fragile gemstones.
When working with gemstones, it’s important to understand that durability is not a single metric defined by hardness alone. Stones that rank high on the Mohs hardness scale can still chip, crack, or react poorly to heat and cleaning methods. Before choosing a gemstone, consider the following four factors that determine how a gemstone will perform.
- Hardness – A gemstone’s resistance to scratching and indicates how well a stone can resist surface wear from contact with other materials.
- Toughness – A gemstone’s resistance to chipping, cracking, or breaking when subjected to impact or pressure. Stones with cleavage planes or heavy inclusions may have lower toughness, even if they rank high in hardness.
- Stability – A gemstone’s ability to withstand heat, light, chemicals, and environmental exposure. This factor is especially important during bench work, such as soldering, polishing, and cleaning.
- Durability – The overall ability of a gemstone to withstand wear over time. Durability is determined by the combination of the above factors.
Understanding these distinctions allows jewelers to make informed decisions regarding the amount of delicacy that must be used when handling. Let’s take a look at common fragile stone types to better understand how to work with them.
Common Fragile Stone Types
Emeralds
Emeralds, known as one of the “Big Three” of the gemstone world have been favorites for decades for their vibrant rich green color. Emeralds are also well-known for their internal inclusions, often referred to as jardin. These inclusions are not flaws but characteristics, although they significantly reduce toughness. It’s important to remember that most Emeralds are routinely fracture-filled with oils or resins, which improves clarity but certain fillers reduce stability especially when exposed to extreme heat.
Mohs Rank: 7.5–8
Bench Risks:
- Fractures expanding under pressure
- Damage during ultrasonic/steam cleaning
- Heat affecting clarity treatments
- Edge chipping at facet junctions
Best Practices:
- Avoid ultrasonic and steam, instead use warm water, mild detergent, and a soft brush
- Limit heat exposure, remove stone before major repair when possible
- Tighten prongs in small increments
- Support girdle areas evenly
- Recommend protective mounting styles (bezel, halo, v-prong covering corners)
- Avoid fillers in preference of stones graded “None” or “Minor oil”.
Moss Agate
This gemstone has risen in popularity over recent years due to its characteristic green “moss” inclusions. Moss Agate is a variety of chalcedony (itself a cryptocrystalline variety of quartz) with dendritic inclusions within the stone. These inclusions create uneven internal stress zones with common surface-reaching fractures. Although this gemstone is relatively hard, it requires patience and restraint during setting.
Mohs Rank: 7
Bench Risks:
- Fracture propagation under uneven pressure
- Edge chipping in thinner cabochons
- Stress cracking during aggressive tightening
Best Practices:
- Use caution when using heavy hammer-setting techniques
- Avoid over-tightening bezels, use gradual, evenly distributed pressure
- Cushion with appropriately supportive settings
- Avoid using ultrasonics and steamers, instead use warm water, mild detergent, and a soft brush
Topaz
Topaz is loved for its array of colors and transparency, luster, and light-return regardless of color. Topaz has great basal cleavage which means it can split cleanly along a specific plane. A common misconception about Topaz is that it’s misunderstood as durable as sapphire due to its Mohs ranking, but its cleavage makes it structurally vulnerable to being struck.
Mohs Rank: 8
Bench Risks:
- Sudden splitting from impact
- Cleavage fractures if pressure aligns incorrectly
- Breakage during hammer setting
Best Practices:
- Identify cleavage orientation before setting
- Avoid impact-based tightening, instead use applied controlled, directional pressure
- Consider protective designs for high-impact pieces
Tanzanite
Tanzanite is loved for its saturated blue-violet color, pleochroism (the phenomenon in which a gemstone displays different colors when positioned at different light angles), and vibrant light return. Being softer than quartz which is a component in everyday dust and grime, this does make is more susceptible to abrasion over a lifetime. Similar to Topaz, Tanzanite also has perfect cleavage in one direction making it susceptible to splitting when struck in certain areas.
Mohs Rank: 6–7
Bench Risks:
- Edge Chipping
- Cleavage fractures
- Abrasion during polishing from contaminated polish components
- Sensitivity to ultrasonic cleaning
Best Practices:
- Use gentle tightening techniques
- Avoid high-impact applications
- Recommends bezels or halos for rings
- Avoid using ultrasonics and steamers, instead use warm water, mild detergent, and a soft brush
For a quick reference at the bench, download our chart outlining common gemstones and the appropriate level of care to use when cleaning them.
Best Settings for Delicate Stones
When working with delicate or structurally vulnerable gemstones, mounting style plays a critical role in long-term performance. The goal is to minimize impact exposure, protect vulnerable edges and facet junctions, and reduce direct pressure on areas prone to cleavage or internal fracture. Thoughtful design choices, such as bezel settings, halos, reinforced prongs, and avoiding exposed corners, can significantly extend the life of a delicate stone.
It is equally important to consider the type of jewelry the stone will be set in different types of jewelry and take on different amounts of impact — bracelets and rings experience far more daily impact than earrings and pendants. Selecting the appropriate setting is not just a design decision; it’s a durability strategy.
Educating Your Customers
Clear communication with clients is just as important as proper bench technique when working with fragile gemstones. Educating customers on wearability, maintenance, and potential risks will set realistic expectations and prevent future dissatisfaction. Many clients associate higher price with greater durability, so it’s essential to explain that beauty and structural resilience are not always the same. Discuss when to wear certain pieces, how to monitor for early signs of damage, and whether alternative settings or jewelry types may be better suited for their needs.
Setting With Intention
All gemstones come with their own challenges that you, the jeweler, must appreciate. For bench jewelers, understanding the structural importance of each stone is essential to preventing damage during setting and ensuring long-term performance in the finished piece. Evaluating durability beyond hardness, selecting protective mountings, and adjusting setting techniques accordingly are all part of understanding how to work with these gemstones to create jewelry that lasts.
Here at Stuller, we offer an expansive selection to support a wide range of gemstone selection in both natural and lab-grown options to support all your customers’ needs and requests.