Which of the following is NOT a sign of fracture filling?

• A. A flash effect.
• B. Trapped gas bubbles.
• C. Heat-induced surface roughness.
• D. Flow structure.

Answer: (C)

Fracture filling changes how cracks in a diamond look and behave because a glass-like material is introduced into the fissures. You’ll see signs tied to that filling material and how it interacts with the crack. A flash effect is the bright edge or sheen along the fracture where the filling meets the diamond, caused by the refractive difference and the way the material lays in the crack. Trapped gas bubbles are tiny voids within the filling material that can be seen under magnification, indicating the filling wasn’t completely degassed. A flow structure shows patterns or directional lines in the filling that reflect how the material flowed into the crack during the filling process.

Heat-induced surface roughness, on the other hand, is not a standard indicator of fracture filling. It points more toward surface damage or changes from heat treatment itself, not the presence of a filled fracture. So, the absence of heat-induced roughness as a sign helps distinguish fractured-filled stones from those that simply show signs of thermal alteration.