22 



INFRA-RED TRANSMISSION SPECTRA. 



5.02, 5.3, 6, 6.26, and 6.65 /x, is due to Nichols, 1 who used a section 

 0.018 mm. thick. Unfortunately his curve begins in the slight band at 

 4-35 A 1 ; so that there is no check upon its accuracy of location. 



Konigsberger 2 examined smoky quartz and found bands at 3.05 and 

 4.05 /,. Merritt, 3 using polarized light, found bands at 3 and 3.6 /t for 

 the extraordinary ray, and bands at 2.9, 3.75, and 4.1 p. for the ordi- 

 nary ray. 



For amethyst, which is violet quartz, of which the color has been 

 attributed to manganese, Konigsberger found an absorption band at 

 3.1 fi. As a whole, different observers agree in locating a small band 

 near 3 p. which will not interfere in considering water of crystallization. 



60% 



345 



FIG. 6. Heulandite. 



to /*// 



Opal is quartz containing variable proportions of water, from 5 to 30 

 per cent. It shows no traces of crystallization. Neither is it considered 

 a solid solution, for the water contained is not a function of the vapor 

 pressure. The transmission curve of opal has the general outline of the 

 curve for water and contains the bands of water at 1.5, 2, 3, and 6/u,, 

 as well as the silicon bands at 4.2 and 5 p. The 3 and 6 p. bands are 

 the composite of the water and silicon bands in those regions. 



(Section ground parallel to b; f = o.20 and 0.22 mm.; semi-transparent. Fig. 6.) 



Heulandite belongs to a class of minerals called zeolites, 4 which are 

 hydrated silicates of alumina, alkalies, and generally lime. To this class 



1 Nichols : Phys. Rev., 4, p. 297, 1896. 



* Konigsberger : Ann. der Phys. (3), 61, p. 687, 1897. 



'Merritt: Ann. der Phys. (3), 55- P- 49, 1895. 



1 Miers : Mineralogy, p. 483. 



