COLUMBATES, PHOSPHATES, VANADATES 



511 



PYROMORPHITE 



Pyromorphite. Pb 6 Cl(P0 4 )3; Chloro-phosphatc of lead; - JM><) 

 = 82.3, Cl = 2.6, P 2 O 6 = 15.7; Hexagonal; Type, Hexagonal 

 Equatorial; c = .7362; 0001 A 1011 = 40 22'; 0001*2021 =_59 

 32'; Common forms, c (0001), m(1010), x(1011), y(2021); 

 Cleavage, m and x in traces ; Brittle ; Fracture, conchoidal ; 

 H. = 3.5-4 ; G. = 6.9-7 ; Color, shades of green, yellow, or brown ; 

 St ivak, white or pale ; Luster, resinous ; Subtranslucent to nearly 

 opaque; o> = 1.51; c = 1.45; <o = .QP6; Optically ( ). 



B.B. Fuses easily at 3.5. With soda and borax in R. F. on 

 coal yields lead buttons and a lead coat. Dissolves in HN0 3 , 

 yields a yellow precipitate with ammonium molybdate. When a 

 S. Ph. bead is saturated with copper oxide and heated with the 

 powdered mineral it shows chlorine. Some specimens may con- 

 tain arsenic. 



FIG. 516. Pyromorphite from Baumbach, Prussia. 



General description. Crystals are columnar, striated length- 

 wise, usually hexagonal prisms roughly terminated or pitted at the 

 termination. In rare cases they are terminated by the pyramid 

 and base, as at Causthal in the Harz. Crystals from Ems, Nassau, 

 are terminated by the base only. Also in parallel growths, irregu- 

 lar aggregates, or granular ; sometimes in amorphous crusts and 

 concretions. 



Pyromorphite is a secondary mineral formed by the interaction 

 of water containing phosphates in solution and lead ores. It is 



