American Gemological Laboratories (AGL) has announced changes in its reports and disclosure terminology for heated rubies, which can more accurately describe healing of fissures during the heating process of rubies. In the modifications, the previously used term “Inorganic (fluxtype)” has been replaced with “Heating residues”, and there is a new statement added that “Heating residues are deposited along healed fractures during the heating process” under the comments section of all of AGL’s grading reports.

The term “Clarity: Inorganic (fluxtype)” used by AGL described the effect of heating on rubies upto the point when rubies upon being heated, are usually coated with a variety of fluxing agents, which melt with increase in temperature and partially dissolve the ruby’s surface, allowing for healing of fissures. This ultimately seals and reduces the appearance of the fissures and improves the general durability of the stone, as described by AGL’s term: “Clarity: Inorganic (fluxtype)”, with additional terminology that addressed the relative quantity of material that remained (e.g. faint, moderate, etc.).

The term “heating residues” came into existence and was popularly adopted by laboratories across the world, as the effects of heating were being understood more deeply. In reality, using fluxing agents during heating results in a combination of features or materials being deposited and remaining along the newly healed fissures. The previously open fissures are replaced by planes consisting of regrown ruby (synthetic), solidified vitreous melt (glass) and voids (empty bubbles). The relative amount of these three parts depends on many factors which are described in “heating residues” and terms describing the relative quantity (such as: minor residues in fissures).

Prior to heating, rubies are coated with fluxing agents. As temperatures rise during the heating process these fluxing agents melt and enter surface reaching fissures. As the ruby cools at the end of the heating process, tiny amounts of ruby (corundum) is regrown healing and bonding the fissures. Also remaining confined to the newly healed fissures are solid vitreous melts and tiny voids.

The term ‘heating residues’ describes the combination of regrown ruby, glass and empty bubbles along the healed fissures. Along with the term ‘Heating residues’, AGL has also incorporated an additional description under the comments section of all Prestige and FastTrack reports, stating: “Heating residues are deposited along healed fractures during the heating process.”