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Infrared FTIR absorption spectroscopy in corundum: 3309 cm-1 hydro-grossular peaks?

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E
Elena Spectra•910 rep

What molecular hydrogen-defect absorption bands in the infrared spectrum confirm low-temperature heat treatment in blue sapphires?

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5 Answers from travellers

✓Accepted Answer

Fourier-Transform Infrared (FTIR) spectroscopy is the definitive laboratory method for detecting low-temperature thermal enhancement (600-900°C) in natural corundum. Unheated natural blue sapphires typically show a clean infrared transmission window around the 3309 cm-1 region. When stones are heated—even at low temperatures designed to heal surface fractures without dissolving internal rutile silk—water molecules dissociate, and hydrogen ions enter structural vacancies, generating a distinct series of sharp absorption peaks centered at 3309 cm-1 alongside associated peaks at 3232 cm-1 and 3186 cm-1.

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D
Dr Kularatne Lab•1950 rep

A beam condenser accessory on the FTIR spectrometer focuses infrared light directly through small faceted culets to resolve clean absorption spectra.

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E
Elena Spectra•910 rep

Natural untreated stones can occasionally display weak 3309 peaks if they originate from specific metamorphic fault environments, requiring microscopic corroboration.

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L
Lars Crust•915 rep

International gemstone certificates issued by Gübelin or GIA reject stones displaying low-temperature treatment indicators unless explicitly disclosed as heated.

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M
Max Rigging•925 rep

Surface-reaching fractures healed with foreign glass fluxes exhibit distinct epoxy absorption bands in the near-infrared region.

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C
Clara Gastronomy•885 rep

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