12 



INFRA-RED REFLECTION SPECTRA. 



8.5 and 9 fi could be detected. The reflecting power is low, which is no 

 doubt due to the presence of the silicate. The maxima at 6.65, 7.3, and 

 7.8 y. are in common with those of malachite. The transmission curve of 

 azurite is given in the preceding volume. It shows the OH band at 3 \i 

 and the carbonate bands at 3.5 and 4 \i. 



Dolomite [CaMg(C0 3 ) 2 ]. 

 (A plane cleavage piece. From Traversella, Italy. Curve a, fig. 4.) 



Dolomite is of interest because it is a double carbonate of Mg and Ca. 

 The reflecting power is high. The first band is in common with that of 



50% 



40 



C 

 .2 30 



'w20 

 cc 



10 



> 5 6 1 8 



Fig. 4. Dolomite (a); Siderite. 



IOJU 



CaC0 3 , while the second band is to be found in MgCOo. The maxima 

 occur at 6.58 and 6.95 fi. 



Siderite (FeC0 3 ). 

 (Cleavage piece. From Allevard, France. Curve b, fig. 4.) 



The reflection curve of siderite is composed of a complex maxima 

 similar to that of dolomite. The maxima occur at 6.6 and 7.1 /. 



Fig. 5. Calcite (a); Magnesite. 



Calcite (CaCOa). 

 (Curve a, fig. 5.) 



The reflection curve is obtained from a natural cleavage face of Iceland 

 spar. The reflection band is complex with maxima at 6.6 and 6.85 fi. 

 The reflection bands in the deep infra-red will be noticed presently. It is 



