SIXTH REPORT OF THE DIRECTOR IQCQ 



197 



CONTRIBUTIONS TO MINERALOGY 



BY H. P. WIIITLOCK 



Brookite 



Indian Ladder, Albany co. 



Brookite from a new locality in the Helderberg escarpment was 

 noted on a specimen of calcite collected by Mr C. A. Hartnagel. 

 Subsequent examination of the locality resulted in the collection of 

 a suite of specimens of calcite which yielded on solution 10 small 

 crystals of this mineral. The calcite vein from which these were 

 obtained is situated at a point about 

 half way up the cliff about 2 miles 

 south of Meadowdale and ^2 mile 

 east of the road which ascends the 

 escarpment from the latter village. 



The crystals are minute, measuring 

 from I milHmeter to .5 millimeter in 

 length. They are in every instance 

 brilliant, with sharp, well defined 

 faces and in general habit resemble 

 those from Ellenville, Ulster co., 

 N. Y. Figure i a and b shows the 

 prevailing crystal habit. The vertical 

 zone is much striated, due apparently 

 to the development of vicinal pris- 

 matic forms. The following forms were noted on the seven crystals 

 which were measured : 



a(ioo), c(ooi), k(4io), 1(210), m(iio), y(i04), t(o2i), 

 z(ii2) and e(i22). 



The following measurements served to identify the forms: 





/r 



X==r— — ^ 





t< 



■:^ 



/ 



r 





y 





< 



\ 









a 



h 



I 





m 



Fig. I Bookite, Indian Ladder 







NUMBER OF 







LETTER 



ANGLE 



READINGS 



MEASURED 



CALCULATED 









/ 



/ 



m : m' . . . 



110 : no 



13 



99 46 



99 50 



1:1'.... 



210 : 210 



9 



134 21 



134 21i 



k :k'.... 



410 : ilO 



10 



155 54 



156 14 



c : y 



001 : 104 



7 



15 37 



15 40 



c : t 



001 : 021 



15 



62 5 



62 6) 



z : z'''... 



112 : 1T2 



4 



44 25 



44 461 1 



z : z'.... 



112 :T12 



6 



53 44 



53 48 v' 



e : e"'. .. 



122 : 122 



4 



78 38 



78 57i/ 



e :e'.... 



122 : T22 



5 



44 19 



44 23J 



