Water in beryl — a contribution to the separability of natural and synthetic emeralds by infrared spectroscopy

Hydrothermal Synthetic Red Beryl from the Institute of Crystallography, Moscow

“…A comparison of midinfrared (6000-400 cm -1 ) spectra for representative natural and synthetic red beryls (figure 16) reveals absorption features that have been reported previously in hydrothermal synthetic beryls (see Schmetzer and Kiefert, 1990;Henn and Milisenda, 1999). The natural crystal displays almost no absorption features above 2300 cm -1 , except for several weak features between about 3000 and 2800 cm -1…”

“…To compare our data with those published by Schmetzer and Kiefert (1990) for natural and synthetic beryls, we recorded an infrared transmission spectrum for fragments of one synthetic red beryl crystal. These fragments were embedded in powdered potassium bromide (KBr) and then formed into a thin pellet for analysis.…”

“…This latter feature in the spectrum of synthetic red beryl, and its absence in the spectrum of the natural counterpart (which contains very little water), is the most distinctive difference in infrared spectra, and it provides immediate proof that the material is a hydrothermal synthetic. Schmetzer and Kiefert (1990) grouped natural and synthetic emeralds into five categories based on the relative intensities of the water-related midinfrared bands at 3694, 3592, and 3655 cm -1 (which they labeled as bands A, B, and C, respectively). The relative intensity ratio of these three bands in the synthetic red beryl is A>B>>C. This result is consistent with the group II spectrum type, which Schmetzer and Kiefert (1990) suggested is typical of other low alkali-bearing synthetic beryls and synthetic emeralds grown in Russia.…”

“…Again, this very low water content may contribute to the low R.I. values. The synthetic red beryls examined for this study were not analyzed quantitatively for water, but they contained sufficient water for it to be readily detectable by routine mid-infrared spectroscopy techniques, as is typical of any hydrothermally grown synthetic beryl (see Schmetzer and Kiefert, 1990). (Sinkankas, 1981;Deer et al, 1997).…”

Confocal Micro-Raman Spectroscopy: A Powerful Tool to Identify Natural And Synthetic Emeralds

“…This method provides some distinct advantages over previous techniques. For example, traditional FTIR analysis requires that 2 mg of material be pulverized and mixed with KBr powder (Schmetzer and Kiefert, 1990), and then the powder needs to be pressed into a thin disk, making this a destructive and time-consuming technique. Microscopic determination requires a trained and experienced gemologist, and is only effective if the sample contains diagnostic inclusions.…”