SIXTH REPORT OF THE DIRECTOR I909 



197 



CONTRIBUTIONS TO MINERALOGY 



RY H. P. WHITLOCK 



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 j4 mile 

 east of the road which ascends the 

 escarpment from the latter village. 



The crystals are minute, measuring 

 from 1 millimeter to .5 millimeter in 

 length. They are in every instance 

 brilliant, with sharp, well denned 

 faces and in general habit resemble 

 those from Ellenville, Ulster co., 

 N. Y. Figure 1 a and b shows the 

 prevailing crystal habit. The vertical 

 zone is much striated, due apparently 

 to the development of vicinal pris- Fi ^- T Bookite, Indian Ladder 

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

 which were measured: 



a(ioo), c(ooi), k(4io), 1(210), m(no), y(i04), t(o2i), 

 z(ii2) and e(i22). 



The following measurements served to identify the forms: 



/h 



S=r~ 



c 





- — 



-\ 





f 



y 





}j~ 





t< 



< 



h 









a 



h 



I 





m 



LETTER 





ANGLE 



NUMBER OF 

 READINGS 



MEASURED 



CALCULATED 









/ 



/ 



m : m' . . . 



110 : T10 



13 



99 46 



99 50 



1:1'... 





210 : 210 



9 



134 21 



134 214 



k :k'... 





410 : 410 



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 : 112 



4 • 



44 25 



44 4611 



z : z' . . . 





112 : T12 



6 



53 44 



53 48 k! 



e : e"'. . 





122 : 122 



4 



78 38 



78 57j] 



e : e' . . . 





122 : 122 



5 



44 19 



44 23J 



