A rough diamond is a product of extreme environment—forged hundreds of kilometers deep within the Earth’s mantle under massive pressure and heat. While this process creates the hardest natural material on earth, it can also trap a hidden danger inside the stone: internal tension.
For the polishers and cutters at S. Muller & Sons, identifying and managing this tension is a critical part of the manufacturing process. Failing to do so can result in catastrophic damage to the stone and physical danger on the factory floor.
What Causes Internal Tension?
Internal strain in a rough diamond is typically caused by anomalies during its crystallization process billions of years ago.
- Inclusions: Foreign minerals (like garnet or diopside) trapped inside the diamond have different thermal expansion coefficients than the surrounding carbon lattice. As the diamond traveled to the surface and cooled, these inclusions contracted at different rates, creating localized stress fields.
- Structural Distortion: Irregular growth patterns or plastic deformation deep within the earth can warp the crystal lattice, leaving the stone under permanent microscopic strain.
The Danger on the Wheel
Diamond polishing relies on friction. When a rough diamond is pressed against a cast-iron scaife rotating at thousands of RPMs, it generates intense heat and vibration.
If a cutter attempts to polish or saw a diamond with high internal tension without accounting for it, the results are immediate. The combination of friction, heat, and structural stress can cause the diamond to release its tension all at once. The stone can crack, cleave uncontrollably, or in severe cases, shatter violently on the wheel.
This not only destroys the value of the rough stone instantly, but flying diamond shards pose a serious safety risk to the polisher.
How We Detect and Manage Strain
At S. Muller & Sons, we do not leave internal tension to chance. Before a stone ever touches a blade or a scaife, it undergoes rigorous analysis.
- Polariscopes: We examine the rough under polarized light. Because strain distorts the crystal lattice, it changes how light travels through the stone. Under a polariscope, internal tension reveals itself as distinct, colorful interference patterns (birefringence).
- Laser Mapping: Old school traditional mechanical sawing is too risky. We use advanced laser scanning and cutting to map the safest planes and slowly relieve the stone’s internal pressure without physical friction.
- Experience: The eye of the polisher will determine if it’s safe to go ahead and polish the diamond, or if it is too dangerous.
Learn more about our manufacturing processes and diamond inventory at muller.be.