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GEOLOGY AI^D MINIlS'G IXDCTSTRY OF LEADVILLB. 



Analysis XLII. Shaft accretion— Coutiuned. 

 Portion iiisoluhJe in ocids. 



Elementary analysts. 



Eational analysis. 



Per cent. 



Silica lO.lOOOOOO 



Oxide of lead 0.4050000 



Oxide of zinc 0.3000000 



Oxide of iron 1.1000000 



Oxide of mnnganese Trace 



Alumina 1. 6000000 



Lime 2.1000000 



Magnesia 1.0050000 



Loss 0.1171501 



Total 100.0000000 



Per cent. 



Silica 10.1000000 



Oxideoflead 0.4050000 



Oxideofzinc 0. SOOOOOO 



Oxideotiron 1.1000000 



Oxide of mangauese Trace 



Alumina 1.6000000 



Lime 2.1000000 



Magnesia ■ 1.0950000 



Loss 0.1171501 



Total 100.0000000 



Silver, 22 ounces to the ton ; gold, trace only. 



Discussion. — The points of interest in this aual^'sis are fbe concentration of phos- 

 phoric acid in the form of phosphate of lime, the presence of caustic limp, and the 

 presence of 22.3 per cent, of metallic lead in an impalpable form. A glance at the 

 whole analysis shows the close resemblance between accretions and chamber dnst, 

 the former representing products of sublimation, the latter products of volatilization. 



Assays of normal accretions — The writer prepared a sample of accretions identical 

 in appearance with the one reported above and made up of twelve specimens from the 

 following smelters : 



C'umuiiug & Finu * 



Grant t 



Harrison 1 



Gage, Hagaiuau & Co , 3 



Total lumiber of specimens mixed for ass.ay 12 



The powder ami grains in this mixture were separated, as usual, by the sieve. 



The whole accretion assayed 21.1092 ounces of silver to the ton. The specimen 

 analyzed assayetl 22 ounces, showing a remarkable uniformity in the composition of 

 these products from various sources. The accretion powder assayed 21 ounces and the 

 accretion grains 23.6 ounces of silver to the ton. This last figure is very interesting, 

 as showing the contents in silver of volatilized bullion. There can be no doubt about 

 this, since the accretions assayed eome precisely from smelters which run the riche.-t 

 and the poorest bullion ; besides, if we consult the assays of lead grains fonnd in other 

 jjroducts (the mattes and hearth accretions, for instance), we find that in no instance 

 do lead grains contain so little as 23 ounces of silver. 



In connection with the normal accretions just described will be given the assay 

 of common accretions, whicli differ entirely from the preceding. Instead of being- 

 light and porous, they are very heavy and compact, and consist either of galena which 

 has escajied reduction or of artificial galena formed in the furnace b.y the reduction of 



