SILICATES. 



99 



position of the absorption band. The band at 4.1 and 4.5 /x are in common 

 with the other feldspars. 



Orthoclase (Feldspar) [KAlSi 3 8 ]. 



(Rod 7 by 2.2 mm. Energy, 7.5 watts. Curve a, fig. 65. Transmission, Carnegie Publica- 

 tion No. 65, p. 64.) 



This sample was translucent, due probably to air-bubbles. Its color 

 on 7.5 watts was slightly red, due in part to reflected light from the elec- 



3 4-56 



Fig. 66. Oligoclase. 



trodes. The emission bands at 2, 2.88, 4.1, and 4.5 /* are in common with 

 the preceding, with the possibility of a small band at 3.1 p., to be noticed 

 in fig. 66. 



