54 



INFRA-RED TRANSMISSION SPECTRA. 



GLAUBERITE (Na 2 SO*CaSOO. 

 (Monoclinic; cleavage section parallel to c; transparent ; t = 1.26. Curve b, fig. 39). 



This is a mixture of two sulphates, of which the CaSO 4 band at 3.2 

 and 4.55 /A have already been noticed. Glauberite has bands at 3, 4.55, 

 5.6, and 6.2 /*. 



THENARDITE (Na 2 SO 4 ). 



(Borax Lake, California. Orthorhombic ; ground parallel to c; f = 2.2 mm. 



Curve a, fig. 40.) 



This mineral was too brittle to grind successfully. It shows large 

 bands at 3.1 and 4.55 p. 



0/234567 



FIG. 40. Theuardite (a) ; Kieserite. 



KlESERITE(MgSO 4 ). 

 (Stassfurt Mines. Massive; subtranslucent ; ( = 0.22 mm. Curve b, fig. 40.) 



This mineral, like selenite, shows both water and SO 4 bands. It is 

 very opaque. The water bands at 1.5, 3, 4.55 (complex with SO 4 ), 

 and 6.05 p are prominent. There are two small bands at 1.8 and 7^, 

 respectively. 



CELESTITE (SrSO<). 



(From Lampasas, Texas. Cleavage parallel to c; transparent; t = 0.67 mm. 



Curve a, fig. 41.) 



Celestite has absorption bands at 3.2, 4.55, and 6.4/1,. The 4.55 /u, 

 band is conspicuous for its depth. 



ANGLESITE (PbSO<). 



(Monte Poni, Sardinia. Translucent; section parallel to m; ( = 0.7 mm. 



Curve b, fig. 41.) 



The section used was not quite long enough to cover the slit. The 

 lack of transparency was in part due to the fact that on account of its 



