Bowles — P yromorphite from British Columbia ^ Can. 43 



Yellow Variety Green Variety 



PbO 80*20$ 80-13$ 



CaO ._. 0-59 0-56 



FeO... 0*86 0-46 



P 2 5 16-12 15-65 



As 2 5 0-41 0-90 



Cl 2 2-52 2-59 



CaF 2 trace 



Insol 0-08 0*05 



100-78 100-34 

 Less oxygen equiva- 

 lent ofCl 0-57 0-59 



100-21 99-75 



Although there is considerable difference to be observed in 

 the results of these two analyses, such as the striking variation 

 in the amounts of iron and arsenic, it can, nevertheless, be 

 shown that the analyses are to be relied upon ; for if the mole- 

 cular ratios are calculated from the above determination, it will 

 be seen that in each case the results point to the generally 

 accepted formula for pyromorphite. 



Yellow Variety Green Variety 



Molecular Eatios Molecular Eatios 



I II III I II III 



PbO _. 0*324 ) 0-323 ) 



CaO.. . __:. 0-010 \ 0-346 9'03 0*010 \ 0*340 8'95 



FeO... 0-012 ) 0-007 ) 



P 2 5 0-013) 3-00 0-110) 3-00 



\ 0-115 [ 0-114 



As 2 0_ 0-002 ) 0-004 ) 



PbCl 2 036 0-036 0*94 0'037 0*037 0*98 



Since the combined molecular ratios of the oxides of lead, 

 calcium, and iron, and the pentoxides of phosphorus and 

 arsenic, are almost exactly in the proportion 3 to 1, we may 

 assume that those values are very nearly correct. Hence if we 

 give to the combined ratios of the pentoxides of phosphorus 

 and arsenic the value 3, we obtain the simplified ratios in 

 columns III. In each case these are approximately 9:3:1, 

 which, as remarked above, is in close agreement with the 

 generally accepted formula 9Pb0.3P 2 5 .PbCl 2 , or in more 

 simplified form Pb 5 Cl(P0 4 ) 3 . 



In some cases the green color has been accounted for by the 

 presence of a small amount of copper, but here no trace of 

 copper is to be found. Leonhard* states that the yellow 

 *N. Jahrbuch fur Min. und Geol., 1867, p. 449. 



