MISCELLANEOUS COMPOUNDS. 



OUCOCLASK 



(From Bakersville, North Carolina. Cleavage piece; not polished; transparent; 



f = 1.25 mm. Curve a, fig. 52.) 



This mineral has no marked absorption bands. There is a depression 

 in the transmission curve at 3.3 /A. 



ORTHOCLASE (var. ADULARIA) (KAlSinOs). 



(From St. Gothard, Switzerland. Cleavage parallel to c; perfectly transparent; 



* = O.I5 mm. Curve b, fig. 52.) 



The transmission curve shows bands at 2.0, 3.2, 3.9, 4.8, and 5.6^, 

 and is in marked contrast with the orthoclase curve. 



ZIRCON (ZrSiCu). 



(Transparent; f = 3 mm. Curve c, fig. 52.) 



This specimen was not long enough to cover the slit. It shows bands 

 at 2.1, 3.1, and 3.6 /x, and complete opacity beyond 5 /A. 



90 



80 



o 



60 



50 



JO 



10 



\ 



\ 



\ 



IZ 13 



14 



O I ^ 3 <? 5 6 7 8 9 10 II 



p IG . 53. Glass (a) ; Albite (b) ; Bnstatite (c). 



GLASS. 



(Microscope cover-glass; f = o.og mm. Curve d, fig. 52; curve a, fig. 53. 



t = 0.00 1 mm.) 



The transparency of glass is very great up to 2 p. The curve shows 

 a depression at 3.2 /*, and bands at 5.6 and 6.25 /*, which are common to 

 SiO 8 compounds. For this thickness glass is transparent to 8 /*. 

 5 c 



