The H(b) code in Lotus Gemology's disclosure framework denotes a heated stone that shows minor residues in surface-reaching fissures or cavities, consistent with traditional borax-fluxed heat treatment. The stone has been heat-treated to improve colour and clarity, and during the heating cycle a small amount of flux has migrated into existing fractures, leaving a detectable but limited residue.

What H(b) reflects in practice

Traditional heat-treaters in Bangkok, Sri Lanka, and Burma have used borax and other fluxes for decades to heal surface fissures during the heating cycle. The flux acts both as a fluxing agent for the silica that closes the fracture and as a means of reducing surface frosting on the cooled stone. The flux that remains within the fissure after cooling is, in the H(b) class, limited and subordinate to the host stone's natural material.

How it differs from H(c) and lead-glass filling

The H(b) classification is reserved for stones where residues are minor and incidental to the principal effect of the treatment, which remains thermal. Where the residues are extensive, persistent, or visibly fill significant fissures, the call escalates to H(c). Where filling material is structural to the stone's apparent clarity - as in lead-glass-filled ruby - the disclosure leaves the H-series and is described separately as a composite or fracture-filled stone.

Pricing implications

An H(b) ruby or sapphire trades in the same broad commercial band as an H(a) stone, with a modest discount reflecting the residue. The discount widens at the top end of the market, where the most discriminating buyers prefer H(a) for cleanliness of disclosure. At the auction level, both H(a) and H(b) are commonly sold without explicit price differentiation, with the residue noted in the description.