Penfield and Foote — Clinohedrite. 291 



the relations of the forms did not become wholly clear until 

 the crystals from Mr. Hancock's specimen had been studied. 

 Some of the crystals were 3 mm in diameter, and figs. 3 and 4, 

 drawn in the same position as fig. 2, will serve to exhibit the 

 curious habit which they present. 



The position which has been adopted seems well suited for 

 representing the forms of the crystals which are given in the 

 following table : 



5,010 n, 120 jo, HI r, 331 0,131 



A, 320 /, 130 p lt 111 s, 551 o l9 131 



m, 110 e, 101 q, 111 t, 771 x, 131 



m v 110 e xi 101 q l9 111 w, 531 y, 121 



The form 2, figs. 3 and 4, is probably 161, but no measure- 

 ments could be obtained from it. 



The axial ratio was derived from the measurements marked 

 by an asterisk in the accompanying table, and is as follows : 



a:b:c= 0-6826: 1 : 0-3226, 0= 100^001 = 76° 4' 



Following is 



a 



list 



of measurements 



with the calculated 



angles : 











Calculated 



Measured 







Calculated. 



Measured. 



angle on 

 6, 010. 



angle on 

 6, 010. 



m^ra, 110/sllO 



= 



67° 



■2' 



66° 57' 



56° 



29' 



56° 29'* 



/i/s A, 320^320 



= 



47 



38 







66 



11 



65 5 



n^n, 120^120 



= 



105 



54 







37 



3 



37 12 



I a I, 130^130 



= 



126 



34 



_ 



26 



43 



26 55 



p^p, 111^111 



= 



29 



8 



29 8* 



75 



26 







tf/s tf, lll^lll 



= 



34 



52 



34 49 



72 



34 



72 36 



r /\ r, 331^331 



= 



63 



15 



62 56 



58 



22| 



_ .. _ _ 



s /\ .9, 551 /\551 



= 



67 



43 



67 43 



56 



8* 



56 20 



t /v t, in /s 771 



= 



68 



32 





55 



44 







u^ w, 531/s531 



= 



43 



52 



44 6 



68 



4 



68 



93 /s a;, 131^131 



= 



75 



52 







52 



4 



51 56 



y^y, 121/^121 



= 



54 



56 







62 



32 



_ 



/> A e, 111^101 



= 



14 



34 



14 36 









m^p, 110/vlll 



= 



51 



54 



51 54* 









jt?y\2, Ill/sill 



= 



58 



37 



58 29 









^A^, 111^331 



= 



36 



21 



36 20 









r zv s, 331 /s 551 



= 



12 



45 



12 44 









s /s £, 551 /s 77 1 



= 



5 



50 



5 47 









y^e a , 121 A 101 



z= 



27 



28 



27 42 









6 />, 0, 010^131 



= 



46 



43 



46 43 









The cleavage is perfect parallel to the pinacoid b, 010, but is 

 not often observed. The hardness is 5*5 and the specific 

 gravity 3*33. Many of the crystals are transparent, and the 

 color varies from amethystine to nearly colorless or white. 



