All diamonds submitted to GCAL for certification are thoroughly examined to assure the detection of any treatments. A diamond treatment is any artificial process that alters the appearance of a diamond. Any treatments detected are listed under the Color and Clarity grades respectively.

GCAL's research lab is comprised of advanced state-of-the-art instruments along with classic gemological equipment. There are only a handful of gemological laboratories in the world that are so well equipped to detect treated and synthetic diamonds.

One example of a clarity treatment is laser drilling. The purpose of laser drilling is to lessen the visibility of an inclusion. This is achieved by using a laser to create channels reaching from an inclusion to the surface of a diamond. After the channel is drilled, the diamond is soaked in an acid to either bleach or dissolve the inclusion. This treatment typically has a significant affect on value.