lTtt W. T. SchalUr and F. L. Eansome — Bismite. 



The results show that the mineral is either bismite or else a 

 hydrous oxide of bismuth. If the latter be the case, the min- 

 eral is a new species (providing, of course, that Bi 2 3 is the 

 correct formula for the bismuth ocher found in nature and 

 called bismite). Attempts to isolate a sufficient quantity of 

 the pearly scales from the gangue for separate analysis were 

 not successful. 



The minute, tabular crystals are too incomplete to allow of 

 a determination of their geometrical form by crystallographic 

 measurements alone. From the uniaxiality of the crystals, 

 their hexagonal outline, triangular markings on the base and 

 distribution of the faces as far as seen, reference of them to 

 the rhombohedral division of the hexagonal system appears 

 to be justifiable. - 



The value of the c axis, derived in a manner presently to be 

 described, is 0'5775. Seven faces are determined as present ; 

 the base, five positive and one negative rhombohedra. Besides 

 these, there are indications of two more positive rhombohedra. 

 A brief description of these forms follows. 



c-jOOOl}. Always very large, even, and highly polished. 

 Sometimes shows triangular markings or striae, the faces parallel 

 to these markings being taken as positive. 



o {1016 J. Occurs on two crystals, as broad faces giving, how- 

 ever, poor reflections. One face was considerably striated, 

 giving two signals a degree apart. 



q {1015}. Broad faces giving fairly good reflections. 



u {1014}. Narrow faces, one striated with a fair reflection, 

 and one as a line face giving a very poor reflection. 



Jc {1013} Usually as a line face, striated and giving a very 

 poor reflection. 



? {2025}. A doubtful face, narrow, giving no distinct signal. 



?d {1012}. Another doubtful face, broad, giving no distinct 

 reflection. 



y [2021 }. Line faces, giving exceedingly faint reflections. 



z {0111}. The only negative rhombohedron observed. Very 

 faint line faces, giving no reflection. Its negative position could 

 be determined only on crystal No. 6. 



The measurement of the forms are shown below. 



Meas. ■ Calc. 



(0001) : (1016) 6° 31' . 6° 41' 6° 21' 



' " : (1015) 1 33 7 36 1 36 



" : (1014) 9 31 9 31 9 28 



" : (1013) 12 11 12 26 12 32 . 



13 18 12°-14° 



: (2021) 54° 54° 53 OS 



: (0111) 35° 32|° 33 42 



