No. 2385. CRYSTALLOORAPHIC STUDY OF DATOLITE— SHANNON. 525 



f t (361) occurred as a narrow line, giving a faint though distinct 

 signal on crystal B2 between o(120) and M(T22). The angles 

 measured are: 



(361) Measured ^ = 38° 06' p = 83°2S' 

 Calculated <^ = 38° 15' p = 84° 06' 



A = 0° 09' A = 0°38' 



The form is considered to be well established. 

 g t (362) occurred as a line face yielding a fair signal on crystal 10, 

 as shown in figure 19. The angles are: 



(362) Measured ^ = 37° 55' p = 78°35' 

 Calculated ^ = 38° 13' p = 78° 19' 



A = 0° 18' A = 0° 16' 



This form also is normal in the zone (001) : (120) and is considered 

 to be well grounded. 



hi (3.10.20) occurred on crystal B2 as a bright line yielding a fair 

 signal between a (T24) and #(012). The angles are: 



(3.10.20) Measured ^ = 25° 03' p = 34° 54' 



Calculated ^ = 25° 30' p = 35° 02' 



A = 0°27' A- 0° 08' 



(136) Calculated ^. = 27° 32' p = 35°31' 



A= 2° 29' A= 0°37' 



The form is near (T36), as shown above, but not sufficiently near, 

 the quality of the signal considered, to be assigned to that form 

 As shown by its high indices and its zonal position, the form is 

 " disturbed" and somewhat uncertainly established. 



i x (461) occurs as a distinct line face, giving a dim signal between 

 7r (231) and n (111), as shown in figure 24. The angles are: 



(461) Measured ^> = 48° 06' p = 84° 55' 



Calculated v = 46° 26' p = 84° 49' 



A = 1° 40' A = 0° 06' 



j x (5.6.30) occurs on crystal B5 as a very narrow line face trun- 

 cating the angle between p (T14) and 2 (205), as shown in figure 13. 

 The angles are: 



(5.6.30) Measured <^ = 51°47' p = 22° 22' 



Calculated <p = 52° 31' p = 22°35' 



A = 0°44' A= 0° 13' 



