MINERALS FROM LYON MOUNTAIN, CLINTON COUNTY 



73 



wedges of orthoclase have been driven into the perfectly formed 

 apatite crystal causing a distinct inward curve of the surface around 

 the edges of the puncture and a decided bulging of the material 

 displaced by the injected wedge. The writer has produced a simi- 

 lar aspect in a prism of softened paraffin by gently pressing into 

 its surface a steel wedge. The surfaces of the crystals show natural 

 etchings corresponding in symmetry with the hexagonal pyra- 

 midal group. In general the apatite crystals of this phase resemble 

 those from Natural Bridge and other localities in northern New 

 York. The crystal faces do not admit of accurate measurements 

 by reason of the rounded and uneven character of the surfaces. 

 The forms m (ioio), % (ion) and 5 (1121) were identified with a 

 contact goniometer. 



Secondary apatite occurs in small bright crystals, perfectly 

 transparent and light yellowish green to bluish green in color. The 

 largest of these measured 6 mm in diameter. They show an ap- 

 parent rounding at the termination which renders the determina- 

 tion of the crystal habit a matter of some difficulty. Fair reflec- 

 tions of the goniometer signal were obtained in all zones measured 

 and the forms recorded were noted on all of the three crystals 

 studied. The crystal habit as determined by the relative size of 

 the reflecting surfaces is shown in figures 2/^.-2^0. The following 

 summary shows the results obtained from the measurement of 

 three of the best developed of these crystals. 



SUMMARY OF OCCURRING FORMS, MEASURED AND CALCU- 

 LATED ANGLES 





Form 



Angle 



Measured 



Calculated 













/ 



/ 



c 



oooi 



1010 :oooi 



90 



2h 



90 



m 



IOIO 



1010 :ono 



60 



O 



60 



a 



1 120 



1010:1120 



30 



O 



3° 



r 



1012 



ioio :ioi2 



67 



12 



67 1 



X 



IOII 



1010 :ioii 



49 



42 



49 42 







1010:01 11 



7i 



8i 



71 8 







0111 :iioi 



37 



43 



37 44i 



y 



2021 



IOIO .'202I 



30 



38 



30 3 1 



w 



7o73 



1010:7073 



26 



40 \ 



26 48 



z 



3031 



1010:3031 



21 



25i 



21 27 



s 



1121 



1120 :ii2i 



34 



i7i 



34 T-Ah 







1010 :ii2i 



44 



18^ 



44 17 



M 



2131 



1010 :2i3i 



30 



i9§ 



30 20 



