290 



IF. K. Ford — Mint ml Notes. 



«r(221) varied by If ° from the calculated angle, the form has 

 been listed as doubtful by Hintze.* The same form, however, 

 undoubtedly occurs on this crystal from Franklin and should 

 therefore be considered as definitely established. Its iden- 

 tification rests mainly on the fact that it was proven to lie at 

 the intersection of the two zones: a (100)— n (221) — a (100), 

 and M (110) -c (001)- M (110). The following measurements, 

 although not showing as close an agreement with the calcu- 

 lated values as could be desired, nevertheless serve to confirm 

 the identity of the form. 



c (001) : k (221) = 57° 50' measured ; 51° 0' calculated. 

 a (100) : k(221) : 40° 50' measured; 41° 12' calculated. 



Fig. 2. 



"U 



III. On a Brookite Crystal from Companhia, lengoes, Bahia, 

 Brazil / by W. E. Ford and Freeman Ward. ' 



A suite of brookite crystals from Companhia, Lencoes, 

 Babia, Brazil, was recently presented to the Brush Mineral 



Collection by Dr. H. S. Wash- 

 ington. One of the best devel- 

 oped of these crystals was stud- 

 ied, and as eleven different forms 

 were identified upon it, it was 

 thought, because of this com- 

 plexity of development, to be 

 worthy of a short note. 



The crystal was thinly tabular 

 parallel to the macropinacoid, 

 measuring about O^ 01 " vertically 

 and - 5 cm in the horizontal direc- 

 tion. The macropinacoid faces 

 were vertically striated, but the 

 other faces in the prism zone 

 and the faces of the terminal 

 forms were sharply developed 

 and possessed a brilliant luster. 

 The following forms were iden- 

 tified : a (100), c(001), iV 7 (710), 

 A (410), ?(210), m(110), y(104), 

 ^(043), *(021), z (112), e (122). 

 Fig. 2 shows the crystal in ideal 

 development but drawn so as to represent as nearly as possible 

 the true proportions and relations of the different forms. 



Mineralogical Laboratory of the Sheffield Scientific School 

 of Yale University, New Haven, Conn., 

 June 1, 1911. 



* Handbuch der Mineralogie, ii, 1153. 



Fig. 2. Brookite, Brazil. 



