WATER OF CRYSTALLIZATION. 27 



at 1.5, 2, and 3 /*, while the next two bands are shifted to 5 and 6.2 ju. 

 respectively. Porter, 1 by means of "reststrahlen," located a band at 

 4.84 it. 



APOPHYLUTE (H7KCa4(SiO 3 )8+4/^H 2 O). 

 (Section cut parallel to c; transparent; t = o.il mm. Fig. n.) 



This mineral is entirely opaque beyond 3 p. up to 8 fi, where there is 

 slight transparency. The water bands at 1.5 and 2 //, are almost oblit- 

 erated. 



60% 



3 4- 5 6 7 Q 



FIG. it. Apophyllite (a); Deweylite 



10 



II 



DEWEYLITE 



(Massive; whitish color; subtranslucent in section 0.08 mm. thick. From New 



Rochelle, New York. Fig. u.) 



In the curve, b, for this mineral the small absorption bands are oblit- 

 erated but the bands at 3 ^ and 6 /*, are very strong, which would make 

 it appear that the water is present in the form of water of crystalli- 

 zation. 



THOMSENOLITE (NaCAlF 8 -f-H:>O). 



(Monoclinic; cleavage parallel to c; transparent; f = o.75 mm. From Ivigtut, 



Greenland. Curve a, fig. 12.) 



This mineral was obtained as a mass of small crystals, from which 

 one was obtained having an area of about 4 by 5 mm. This crystal 



1 Porter : Ap. Jr., 22, p. 229, 1906. 



