A practical method for optical spectroscopy of crystals

Abstract

In this article a recently developed method for optical spectroscopic analysis of crystallized substances is introduced. The practical method proposed is non-destructive, and the apparatus required is relatively simple and inexpensive. Principles of optical spectroscopy for the analysis of trace elements in complex crystals are reviewed; essential aspects of this method and other routine methods are compared. Next, the nature, scope, and limitations of the new practical method are discussed, and the information, which can be obtained, is summed up. In essence, the procedure consists of the sequential registration of absorption- and luminescence spectra of the substance to be examined, and the subsequent analysis of both spectra. Details of the apparatus required, and of the analysis procedure are treated in the following section; different methods for obtaining good quality absorption- and luminescence spectrograms are reviewed here. An important feature of the method is the excitation of luminescence with blue radiation; the advantages of its use are critically discussed. Facultative refinements of apparatus and method, making possible polarisation spectrography and topographical spectrography of macrocrystals, are indicated. Requirements for preparations for the purpose of calibration are mentioned. The practical value of the new method is demonstrated by results, obtained in the process of determination of some definite typochemical varieties of the crystallized minerals scheelite, apatite, zircon, spinel and topaz; these varieties are described. Finally, possible applications in the fields of mineralogy, gemmology and geochemistry, chemistry and physics, and even in industry, are reviewed. It is expected, that the proposed method will develop into a practical tool for routine researches in these branches of science.