fracture filled diamonds
Fracture-filled diamonds are usually easily detected - the most obvious signs are the "flash effect". The "flash effect" refers to the bright flashes of color seen when a fracture-filled diamond is twisted in under the microscope in bright field illumination; the color of these flashes ranges from an electric blue or purple to an orange or yellow. The flashes are best seen with the field of view nearly parallel to the filled fracture's plane.
Very small air bubbles can sometimes be detected in the cleavage filling of older stones. Since air bubbles are never present in a natural diamond, this is a sign of treatment.
Another identification feature of large, filled fractures is the color of the glass itself: it is often a yellowish to brownish, and along with being highly visible in transmitted light, it can significantly impact the overall color of the diamond.
laser drilled diamonds
Traditional laser drillings are easy to detect as they appear as a straight channel in the diamond.
The detection of KM treated diamonds is more challenging because of the great likeness of the induced crack to a natural cleavage.
This diamond is laser drilled to allowing acids to the inclusion in the
centre of the picture. This acid bleaches the inclusion. © GIA