C. Palache — Mineralogical Notes. 



255 



(7073) |R 



(7071) 



7R 





T(io-o-Io-i) 



loR 



(23-0-23-7) \ 3 -R 



s (1121) 



2P2r 





£ (1122) 



P2r 



(15 -0-1 5-1) -V-R 



^(2112) 



P21 





t (3253) 



fPfr 



r (4041) 4R 



p (1561) 



-6P|1 



£ (6061) 6R 



(2352) 



-fPfl 



m (1010) ooR 



r (1011) R 



s (0111) -R 



£ (5053) -|R 



The forms t, £, and | 1? which are developed on nearly every 

 crystal examined, seem to be characteristic for the locality. 

 The positive rhombohedrons are variable in different vertical 

 zones on the same crystal but have sharply marked faces which 

 give good reflections. The prism planes are almost wholly 

 replaced by the steeper rhombohedral forms. 



Albite. — Wherever the feldspar -of the enclosing granite 

 reaches the wall of the cavity it is coated with a parallel group 

 of water-clear albite crystals. The crystals are all albite twins, 

 consisting in nearly all cases of a single pair of individuals, and 

 the forms present were determined by measurement to be as 

 follows : 



c (001), b (010), m (110), M (110), /(ISO), z (130), x (101), 

 n (021), o (111), and 8 (112). 



Hematite. — Hematite is seen occasionally as lustrous scales 

 or spangles but more commonly as a red pigment staining the 

 surface of quartz crystals or mingled with the kaolin that 

 coats all the minerals in the cavity. 



Chlorite. — Green crystals of chlorite of tabular habit, rudely 

 hexagonal in outline and with rounded edges, are implanted on 

 quartz and feldspar. 



Kaolin. — Kaolin forms a thin coating on the various miner- 

 als described above. It is finely scaly under the microscope, 

 The kaolin is loosely adherent and when removed leaves the 

 underlying crystals bright and fresh. 



3. Crystal Form of Chalmersite. 



The original description of chalmersite by Hussak* gave 

 somewhat meager data concerning the crystallographic develop- 

 ment of the mineral. The following note results from the 

 study of five well-developed crystals taken from a specimen 

 belonging to the Harvard Mineral Collection from the original 

 locality, the " Morro Velho" mine, Brazil. 



The crystals studied and all those visible on the specimen 

 from which they were detached are untwinned, unlike Hussak's 

 material which is described as commonly in twin or multiple 

 crystals. The crystals are slender prisms, the largest, measur- 



*Hussak, E., Ueber Chalmersit, etc., Centralb. fiir Mineral, 1902, 69. 



