i6 



INFRA-RED REFLECTION SPECTRA. 



SCHEELITE (CaWO-j). 



(Massive. From Armidale, New South Wales. Curve a, fig. 8.) 



The reflection power of this mineral behaves in the usual manner, 

 being low in the region of the spectrum up to n //, followed by a strong 

 complex band of selective reflection, the maximum of which extends from 

 ii. 3 to 12.5 n, the possible single maxima being at 11. 3, 11. 8, and 12.4 /<. 

 The reflecting power is unusually low on the long wave-length side of the 

 reflection band. 



Zircon (ZrSiO*). 



(Near Eganville, Renfrew County, Ontario. Curve b, fig. 8.) 



The specimen examined was a large rectangular cleavage piece, about 

 3 by 3 cm., of brownish color, semitransparent in thin sections. 



Although this is a double oxide of zircon and silicon, the reflection curve 

 is entirely different from the silicates previously studied. The strong band 

 of selective reflection occurs farther toward the long wave-lengths, the 

 single maxima (not well resolved) being at 10.1, 10.6, and 11 with a pos- 



60% 



50 



40 



c 

 o 



"" 30 





20 



10 



6 7 8 9 '0 



Fig. 8. Scheelite (a); Zircon. 



IZ 



13 



I4-/U 



sible band at 11.7 /<. As a whole the reflection curve is exactly the same 

 as that of willemite, Zn 2 Si0 4 , previously studied. In the latter, the bands 

 are well resolved and occur at 10.1, 10.6, 11. o, and n.6/<. From this it 

 would appear that in these two minerals the effect of Si0 2 is different 

 from that found in quartz and in the minerals commonly known as sili- 

 cates, viz, silicates of Ca, Mg, Fe, etc. Some of the latter, however, have 

 the last band lying close to the first band in the present silicates. 



WULFENITE (PbMo0 4 ). 



(Red Cloud Mine, Yuma County, Arizona. Curve a, fig. 9.) 



This is a chrome-red crystal. A natural crystal face, 1.5 by 2 cm., 

 having a high polish, but not perfectly plane, was examined. In spite of 

 this the reflection curve is one of the most remarkable yet found. The 

 band of metallic reflection is almost as strong as quartz. There are two 



