LEAD. 



415 



Composition. Carbonic acid 16.00, oxide of lead 82.00, water 2.00 (Klaproth). It is 

 undoubtedly composed of one atom of carbonic acid and one atom of oxide of lead ; but it 

 often contains minute portions of alumina, silica, etc. Formula PbO.COj. 



Geological Situation. This mineral is usually associated with galena, being found in 

 veins of granite, gneiss and limestone. 



LOCALITIES. 



St. Lawrence County. The lead mines of this county have yielded a good deal of car- 

 bonate of lead in an impure pulverulent form. It is commonly called lead ashes, and con- 

 tains, besides carbonate of lead, some sulphate of lead and carbonate of lime. These salts 

 of lead have undoubtedly been formed by the decomposition of the galena, by the reaction of 

 the carbonates of lime. Neither of these minerals have been found here in a crystalline form. 



A mineral resembling the white lead ore, has also been observed, in small quantities, asso- 

 ciated with galena, at Martinsburgh in the county of Lewis. 



Westchester County. Small prismatic crystals of the white lead ore, with a high ada- 

 mantine lustre, associated with galena, copper pyrites, etc., have been found about a mile 

 south of Sing-Sing.* 



Very well characterized crystals of this mineral were formerly obtained at the Perkiomen 

 mine in Pennsylvania. They have been obtained in abundance at the lead mines in Missouri. 



ANGLESITE. 



[From its occurring in Anglesea, in Cornwall, Eng.] 



Plomb Sulfate. Hauy. — Sulphate of Lead. Cleaveland, Phillips and Ihmison. — Prismatic Lead Spar. Jame- 

 son. — Prismatischer Blei-Baryt. Mohs. — Anglesite. Beiidanl and Shepard. 



Fig. 497. Description. Colour white, grey or yellowish ; sometimes 



green or blue, owing to oxide of copper. Streak white. It occurs 

 regularly crystallized ; also massive, disseminated and pulverulent. 

 Primary form a right rhombic prism. Fig. 497. M on M' 103° 42'. 

 Cleavage parallel with the primary planes. Fracture conchoidal. 

 Lustre adamantine, inclining to vitreous or resinous. Transparent 

 to translucent. Brittle. Hardness 3.0. Specific gravity from 6 . 23 

 to 6.31. Fusible by the blowpipe, in the outer flame, into a white 

 slag ; in the reducing flame, it effervesces, and is reduced to the 



metallic state. It is difficultly soluble in nitric acid, without effervescence, in which it differs 



from white lead ore. 



• Torrey. Annali of the Lyceum of Natural ISttory of New-York. IV. 76. 



