Anhydrite, synthetic

Luminescence of in synthetic alkaline earth sulfates is well known (Folk-erts et al. 1995). In this study, CaS04 Pb shows an emission band with a maximum at 235 nm at 300 K, while the excitation maximum is at 220 nm. The decay curve of the emission is single exponential with a decay time of 570 ps at 4.2 K. The emission spectrum of BaS04 Pb demonstrates a broad band peaking at 340 nm with an excitation maximum at 220 nm, while in SrS04 Pb the luminescence band has a maximum at 380 nm. hi natural barite and anhydrite samples we detected several narrow UV bands, which may be connected with Pb emission, but for confident conclusion additional study is needed. In any case, Pb participation in natural sulfates liuninescence has to be taken into consideration. 

ABSTRACT A rapid and precise X-ray fluorescence method has been developed for the multielement analysis of gypsum and gypsum products. Gypsum specimens are calcined at IOOO°C and then fused with sodium tetraborate flux into flat and transparent disks. The choice of a suitable flux system for the specimen preparation is critical because of a rapid decomposition of anhydrite. CaSO,. in lithium ba fluxes at temperatures above 95O C. This decomposition causes not only visible imperfections in the didi surface but also alters considerably the concentrations of the major elements, calcium and sulfur. The procedure used for a fast setup of ten element analysis of gypsum on the Philips PW-1400 spectrometer utilizing synthetic standards and off-line calculated alpha coefficients is presented. Calibrations carried out with chemically analyzed specimens and their mixtures are compared lo those performed with synthetic standards prepared by blending pure chemicals and anhydrite into the flux. 

The second part of this paper is devoted to the procedure used for a quick setup of ten element analysis of gypsum and gypsum products on the Philips PW-1400 X-ray fluorescence spectrometer, utilizing alpha coefficients. Calibration data obtained with chemically analyzed specimens and their mixtures are compared with those based on synthetic standards prepared by blending pure chemicals with anhydrite. 

The raw materials typically consist of reactive silica, raw silica sand, binder, and an aerating agent. Ground synthetic anhydrite (CaSOa) may also be added to retard the slaking of the lime. 

In addition to the related mineral interferences, other minerals common in building material may present a problem for some microscopists gypsum, anhydrite, bru-cite, quartz fibers, talc fibers or ribbons, wollastonite, perlite, attapulgite, etc. Other fibrous materials commonly present in workplaces are fiberglass, mineral wool, ceramic wool, refractory ceramic fibers, kevlar, nomex, synthetic fibers, graphite or carbon fibers, cellulose (paper or wood) fibers, metal fibers, etc. 

Besides, in certain uses another natural mineral, namely, anhydrite and some synthetic material, are better substitutes of gypsum. These substitutes are discussed as follows. 

M. Murat, Investigation Some Factors Affecting the Reactivity of Synthetic Orthorhombic Anhydrite with Water I. Role of Forcing Cations in Solution , CCR.Vol.17, 1987, p663-639... 

A.O.Jamil, M.Murat, A.El-Hajjouji, Factors affecting the reactivity of synthetic orthormbic anhydrite with water II. Role of superfieial defects. Cement and Concrete Research, 1988,18(1), p74-80... 

C.R.Wilding, B. Mile, AT. Vincent, Effect of potassium and sodium sulphates on the reaction of synthetic anhydrite with water. Journal of Chemical Technology and Biotechnology, 1984,34A 80-90... 

Baumer A, Blanc P, Cesbron F, Ohnenstetter D (1997) Cathodoluminescence of synthetic (doped with rare-earth elements) and natural anhydrites. Chem Geol 138 73-80 Beletti A, Borromei R, Oleari L (1995) Absorption spectra of zircon crystals doped with Cr(IV) ZrSi04 Cr -". Inorg Chim Acta 235 349-362... 

Blanc P, Baumer A, Ceshron E, Ohnenstetter D, Panczer G, Remond G (2000) Systematic cathodoluminescence spectral analysis of synthetic doped minerals anhydrite, apatite, calcite. 

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