MINERALS FROM LYON" MOUNTAIN, CLINTON COUNTY 



57 



with parallel systems of wavy lines due to partial resolution. 

 Several of these etched nodules which were obtained in a calcite 

 ■matrix represented originally detached crystals. These roughly 

 presented the form of oblate spheroids and though extremely 

 rough on the surface reflected back the light from minute smooth 

 surfaces in a manner suggesting the appearance of a cleavage 

 fragment. On orienting one of these nodules in the reflection 

 goniometer, it was found that the reflections from these corrosion 

 surfaces in the circle of the transverse axis gave the angles of the 

 prismatic zone for quartz. Furthermore, on reorienting the 

 nodule, reflections were obtained from corrosion faces correspond- 

 ing to the rhombohedral planes r (icii) and z (oiii) the angles 

 agreeing fairly well with theory, considering the character of the 

 faces measured. 



Secondary quartz occurs with hematite, calcite and byssolite, all 

 of later generation and derived from the re deposition of dissolved 

 primary minerals, in brilliant crystals, transparent and for the 

 most part colorless, but occasionally showing slight smokiness as 

 well as inclusions of scaly hematite and prochlorite. A number 

 of crystals were measured, several of which showed the rhombo- 

 hedron r (4041) and the trapezohedrons x (5161) andg' (io.i.ii.i) 

 the two latter being observed on right-handed crystals. In one 

 instance a right trapezohedron was noted in the zone [0110.1121.- 

 10 11] which gave an angle corresponding to (12. 11. 23. 11) but as 

 the face was not repeated on the same or other crystals, its acci- 

 dental presence was assumed to be due to vicinal development. 

 Figures 2a-2b show this habit. 



The observed forms with the measured and calculated angles 

 are given below: 





Forms 



Angle 



Measured 



Calculated 



m 



IOIO 









r 



IOII 









z 



OIII 





/ 



r 



T 



4041 



1010 14041 



II II 



11 8 



S 



II2I 



1010 :ii2i 



37 5i 



37 58 



X 



5l6l 



1010 :5i6i 



11 58 



12 I 



€ 



IO . I . II . I 



1010 :io . 1 . 1 1 . 1 



6 33 



6 31I 



