d 



M 



a 



M' 



LEAD. 417 



It has been found in small quantities at the Perkiomen lead mine in Pennsylvania, where 

 it is associated with other salts of lead. It occurs in small quadrangular tables with bevelled 

 edges, or with truncated angles. The same mineral, in the form of small tabular crystals of 

 a dark wax-yellow, attached to crystallized quartz, also occurs at the Southampton lead mine 

 in Massachusetts. 



PYROMORPHITE. 



Plomb Phosphate. Ha'Uy. — Phosphate of Lead. Cleaveland and PhiUips, — Rhombohedral Lead-Spar. Jame- 

 son. — Rhomboedrischer Blei-Baryt. Mohs. — Pyromorphite. Beudant and Skepard. 



Tig. 499. Description. Colour usually green or brown, sometimes yellow and 



white. Streak white. It occurs regularly crystallized ; also botryoidab 

 reniform and massive. Primary form a regular six-sided prism. Fig. 

 499 is a secondary form. M on M' 120° ; P on M or M' 90° ; M or M' 

 on d' 150° ; M on (/ or M' on c" 131° 45' ; P on c or c' 138° 30' ; & on 

 c or c" 110° 5' [Phillips). Cleavage parallel with M, and also with c- 

 Fracture imperfectly conchoidal and dull. From translucent to translu- 

 lucent on the edges. Hardness 3.5 to 4.0. Specific gravity 6 . 90 to 

 7.30. Before the blowpipe on charcoal, it melts in the outer flame into a globule, which 

 crystallizes on cooling, and becomes brown ; in the reducing flame, the globule appears 

 bluish, is luminous while hot, and on cooling, crystallizes with large facets of a lighter colour, 

 having somewhat the aspect of mother-of-pearl. It is soluble in nitric acid ; and when a bar 

 of zinc is introduced into the solution, blades of metallic lead are deposited on it. 



Composition. Oxide of lead 78.50, phosphoric acid 19.73, muriatic acid 1.65 {Kla- 

 proth). 



Geological Situation. It occurs in veins in primitive and transition rocks, associated 

 with galena and other ores of lead and of copper. 



LOCALITIES. 



Fine specimens of pyromorphite have been found at a mine about a mile south of Sing- 

 Sing in Westchester county, where it was associated with galena, anglesite, malachite and 

 copper pyrites.* 



The same mineral has also been found at the Perkiomen lead mine in Pennsylvania, and at 

 a lead mine in Lenox, Massachusetts. 



• Annalt of the Lycmn of Natural History of New-York. IV. 77. 



MiN. — Pakt II 53 



