No gemological stresses (e.g. no mutable inclusions) were present, indicating that a heat-strengthening procedure was applied.

H- Enhanced by heat (no residues present)

H(a)-Enhanced by heat – residues insignificant (indication of very small residues within fissures only).

H(b)-Enhanced by heat – minor residues are present (within fissures only).

H(c)-Transitional grade between H(b) and H(d).

Clarity and/or color are enhanced by heat. Residues of glass-like materials are present in cavities and/or in fissures. Enhancements such as ‘type C’ are considered permanent and will always be mentioned on the front page of the report.

H(d)-Enhanced by heat – significant and deep-reaching residues present within fissures and cavities filled with lead glass

H(Be)-Enhanced by heat and light elements (such as beryllium).

Clarity and/or color are enhanced by heat and diffusion of light elements such as beryllium, inducing color zoning by internal migration of trace elements (incl. beryllium) and defects, and formation of color centers

PHT (HPHT)-Enhanced by pressure and high temperature (PHT).

E-Clarity and/or color are enhanced by heat (minor residues of foreign solid materials may be present within fissures and/or cavities).