ORES OF LEAD. 149 



Mrs., and in Yuma County ; in the Castle Dome, Eureka, 

 and other districts, where the ore is worked for the silver it 

 contains. 



The lead of commerce is obtained from this ore. It is 

 also employed in glazing common stoneware : for this pur- 

 pose it is ground up to an impalpable powder and mixed in 

 water with clay ; into this liquid the earthen vessel is dipped 

 and then baked. 



Lead Selenides and Tellurides. 



These various ores of lead are distinguished by the fumes before the 

 blowpipe, and by yielding, on charcoal, ultimately, a globule of lead. 



Clausthalite, or lead selenide, has a lead-gray color, and granular 

 fracture, and is occasionally foliated. H.=2'5-3. G.=7-6-8'8. B.B. on 

 charcoal a horse-radish odor (that of selenium). From the Hartz. 

 There is a lead and copper selenide (Zorgite) which has the sp. gr. 

 7-7*5. A lead-and-mercury selenide (Lehrbachite) occurs in foliated 

 grains or masses of a lead-gray to bluish and iron-black color. 



Altaite, or lead telluride. A tin-white cleavable mineral, with H. =3 

 -3*5, and G.=816. From the Altai Mountains. 



Nagyagite, or Foliated tellurium, is a less rare species, remarkable 

 for being foliated like graphite ; color and streak blackish lead-gray ; 

 H.=r l-lo. G. =7-085. It contains Tellurium 322, lead 54'0, gold 9-0, 

 with often silver, copper, and some sulphur. From Transylvania. 



Antimonial and Arsenical Sulphides of lead. These include Sartorite, 

 Zinkenite, Plagionite, Jamcsonite, Dufrenoysite, Boulangerite, KobeU 

 lite, Meneghinite, Geocronite ; also Brongniardite and Freieslebenite, 

 in which silver is also present, and Stylotypite and Aikenite in which 

 copper is also present. 



Minium. — Oxide of Lead. 



Pulverulent. Color bright red, mixed with yellow. GL = 

 4*6. Composition, Pb 3 4 . Affords globules of lead in the 

 reduction flame of the blowpipe. 



Obs. Occurs at various mines, usually associated with 

 galena, and is found abundantly at Austin's Mines, Wythe 

 County, Virginia, with white lead ore. 



Uses. Minium is the red lead of commerce ; but for the 

 arts it is artificially prepared. 



Plumbic ochre is lead protoxide, of a yellow color. 



Mendipite. Color white, yellowish or reddish, nearly opaque. Lustre 

 pearly. G.=7-7'l. PbCl 2 + PbO= Chloride of lead 38 '4, lead oxide 

 61 6. From Mendip Hills, Somersetshire. Cotunnite is a chloride of 

 lead, Pb Cl 2 , occurring at Vesuvius in white acicular crystals. It con- 

 tains 74 -5 per cent, of lead. 



Plumbogummite. In globular forms, having a lustre somewhat 

 like gum arabic, and a yellowish or reddish-brown color. H. =4-4*5. 



