44 



INFRA-RED TRANSMISSION SPECTRA, 



Siderite (FeCOs). 

 (From Allevardj France. Cleavage piece; < = i.2 mm.; grayish color; translucent 



to transparent. Fig. 27.) 



This specimen was examined in connection with the carbonates pre- 

 viously studied. The complex band, with maxima at 3.4, 3.9, and 4.6 /*, 

 is in common with the other carbonates. In a very thin section of calcite 



25% 



20 



c 

 o 



"</> 



.52 IS 

 



(0 



C 

 /0 



I- 



2 3 4- 



Fig. 27. Siderite. 



6/i 



(CaC0 3 ) this region was resolved into sharp bands, having maxima at 

 3.44, 3.93, and 4.6 ix. This sample furnishes additional proof that the 

 large groups of chemically homologous compounds have similar absorption 

 spectra. 



WULFENITE (PbMo0 4 ). 



(From Red Cloud Mine, Yuma County, Arizona. Deep-yellow color; t = 2.i mm. 



Curve a, fig. 28.) 



This mineral is of interest in connection with a study of the oxides, 

 e. g., Ti0 2 , Si0 2 , etc. The transmission curve a, fig. 24, shows wide 



30 



25 



C20 

 ,0 



V) 



'E 15 

 w 



c 

 <d 



2 3 4-567 



Fig. 28. Wulfenite (a); Phosphorus. 



IOJLL 



absorption bands at 3.15 and 6.5^, and complete opacity beyond 9 /*, 

 where there is a band of metallic reflection. 



