A FTIR spectra collection of a large number of various micro-crystalline (C and CT) and non-crystalline (A) opal samples is here presented. The suite of the investigated specimens consists of the most important natural and synthetic opal samples, with a gemological significance, present on the market today, including both with and without play of color. The opal-C type is clearly identifiable on the basis of the sharp peak at about 620 cm-1, whereas the FTIR spectra of opal-CT and -A differ mainly for the position of the 790 cm-1 SiO band. Other phases, such as i.e. clay minerals, present in opal samples and related to different genesis and localities, can be easily detected by mid-infrared spectroscopy, in addition to X-ray powder diffraction data.
A contribution to the study of FTIR spectra of opals / I. Adamo, C. Ghisoli, F. Caucia. - In: NEUES JAHRBUCH FUR MINERALOGIE-ABHANDLUNGEN. - ISSN 0077-7757. - 187:1(2010 Mar), pp. 63-68. [10.1127/0077-7757/2010/0161]
A contribution to the study of FTIR spectra of opals
I. AdamoPrimo
;
2010
Abstract
A FTIR spectra collection of a large number of various micro-crystalline (C and CT) and non-crystalline (A) opal samples is here presented. The suite of the investigated specimens consists of the most important natural and synthetic opal samples, with a gemological significance, present on the market today, including both with and without play of color. The opal-C type is clearly identifiable on the basis of the sharp peak at about 620 cm-1, whereas the FTIR spectra of opal-CT and -A differ mainly for the position of the 790 cm-1 SiO band. Other phases, such as i.e. clay minerals, present in opal samples and related to different genesis and localities, can be easily detected by mid-infrared spectroscopy, in addition to X-ray powder diffraction data.
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