208 



University of California . 



[Vol. 3. 



sulphate crystallizing with seven parts of water instead of five, 

 as is the case with chalcanthite. 



The mineral Occurs massive, with a crystalline structure, and 

 also as fibrous fragments, differing somewhat in physical prop- 

 erties from the massive variety. Chalcanthite is intimately 

 associated with the massive variety. 



Grysiallographic Characters. — Two incomplete crystals of 

 boothite were obtained which showed, with one or two excep- 

 tions, only one face of each of the forms present. 



The crystals are monoclinic and have the following eight 

 forms : 



Letter. 



Symbol. 

 Gdt. Miller. 



C 







001 



a 



ooO 



100 



m 



00 



110 



t 



— 10 



101 





—30 



301 



TT 



i 



112 



C 



—1 



Til 



a 



— 12 



121 



The angle P was measured directly and is probably fairly 

 accurate. From the average of several calculations of j/ and 

 </ { ), together with P, an axial ratio was calculated which is to be 

 considered as approximate. The calculations gave: 

 a:b:r =1.1622:1:1.5000, P = 105° 36'. 



The angles measured, together with those calculated for these 

 forms, from the axral ratio just given, are quoted below: 



M 



S3 



Symbol. 



Measured. 



Calculated . 



























o 



Gdt. 



Miller. 





P 









P 





1 



c 







001 



90° 00' 



15° 



36' 



90° 00' 



15° 



36' 



2 



a 



co0 



100 





90 



00 







90 



00 



3 



m 



00 



110 



41 10 







41 



47 







4 



t 



— 10 



101 



90 01 



46 



20 



90 



00 



45 



37 



5 





—30 



301 



89 54 



74 



39 





77 



74 



29 



6 



7T 



-i 



112 



27 29 



41 



17 



27 



31 



40 



13 



7 



e 



— 1 



Til 



34 35 



61 



25 



35 



16 



61 



26 



8 





—12 



T21 



i 



19 40 



72 



49 



19 



28 



72 



33 



