18 University of California Publications in Geology. [Vol. 7 



Small crystals with bright reflecting faces also occur in the 

 crevices of earthy masses and as a deposition on the black 

 manganese coatings. The crystals are rhombohedrons with the 

 basal planes in about equal development, so their resemblance 

 to octahedrons and to cubes with the tetrahedron is quite marked 

 ( fig. 7 ) . Some of them have the rhombohedral faces striated 

 while the base is perfect. 



The solutions which precipitated the jarosite contained both 

 the sodium and the potassium sulphates, and it is probable that 

 analyses would show the presence of natrojarosite as well as the 

 normal jarosite and gradations of one into the other. A quali- 

 tative analysis made of the yellow flakes shows them to be jarosite 

 but with considerable sodium. 



Bar it e. — The sulphate of barium does not occur abundantly 

 in the vein, yet masses of crystals covering several square feet 

 are found on the walls of some of the fissures. The crystals are 

 white and have the common basal-plate habit. Some are half an 

 inch thick and an inch or more wide. The large crystals consist 

 simply of the base c (001) and prism m (110), while the smaller 

 ones have also narrow faces of the pyramid z (111), and brachy- 

 pinacoid b (010). Thin layers of hematite or limonite coat many 

 of them. Some of the stout plates are later parallel enlargements 

 of smaller plates and the interior crystal had often the brachy- 

 pinacoid, not present on the outer or enlarged crystal. Figure 8 

 illustrates the type of crystals. 



Measured Calculated 



(110) : (HO) 78°21' 78°22' 



(110) : (010) 50 50 50 49 



(001) : (111) 64 24 64 19 



(110) : (111) 25 42 25 41 



TUNGSTATE AND MOLYBDATE : HUBNERITE OR WOLFRAMITE, AND 



WULFENITE 



Hiibnerite or Wolframite. — The manganese tungstate occurs 

 in black platy masses in the compact quartz gangue and in very 

 thin plates in the cavities and seams of the gangue. All of the 

 material contains iron and is to be classed as wolframite rather 

 than as hiibnerite. The crystals are tabular parallel to the 



