46 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



(4) Cerussite, massive, granular, colored with a little iron. This variety of rr- 

 averages by assay 60.7 per cent, of lead and 8 ounces of silver per ton. (51063.) 



(5) Cerussite, massive, compact. (51061.) 



(6) Cerussite, massive and crystalline, with streaks of oxide of iron. (51060.) 



(7) Cerussite, massive, granular, in gray and black streaks. (51070.) 



(8) Cerussite, crystalline, in layers, a little stained with iron. (51071.) 



(9) Cerussite and anglesite, stained with iron. (51065.) 



(10) Cerussite and anglesite, exhibiting the cubical structure of the original 

 galena. (51066.) 



(11) Anglesite, showing decomposition to cerussite. (51064.) 



(12) Anglesite, very pure, exhibiting in great beauty and perfection the cubical 

 structure of the' original galena, quite a common character of the lump ore. The 

 average of this ore bv assay is 57.5 per cent, lead and 31.1 ounces of silver. A speci- 

 men picked for its purity showed sulphate of lead 99.65 per cent., sesquioxide of 

 iron 0.075 per cent., and silica, arsenic, antimony, copper, zinc, and manganese not 

 present, while the silver varied from 2 to 30 ounces per ton. (51056.) 



(13) Anglesite, inclosing cerussite, a rare occurrence. (51068.) 



(14) Galena, tine grained, fibrous, coated with cerussite, stained with iron; shows 

 also a little iron pyrite and native sulphur. This character of ore averages by assay 

 76.2 per cent, lead, and 12.2 ounces of silver per ton. (51058.) 



(15) Galena, showing decomposition to anglesite and then to cerussite, stained on 

 the outside with iron. (51062.) 



(16) Galena, fine grained and slightly fibrous, showing decomposition to sulphate. 

 This variety of ore averages by assay 67.5 per cent, lead and 27 ounces of silver per 

 ton. (51057.) 



(17) Galena, shows coarse cleavage and is coated by decomposition products. As- 

 says silver 23 ounces per ton. (51067.) 



(18) Native sulphur, a rare occurrence of the decomposition ol' galena. (51069.) 



A single illustration of oxidized siliceous ore is shown : 



(1) Chert, stained with iron. Small Hopes Mine, Leadville, LakeCounty,Colorado. 



(51052.) This ore is of the following composition : 



Iron (Fe) varies from 25 to 38 per cent. 



Silica (Si O,) varies from 27 to 57 per cent. 



Lead (Pb) varies from to per cent. 



Silver (Ag) varies from 80 to 210 ounces per ton. 



The basic sulphide ores are represented by three specimens : 



(1) Galena, blende, and pyrite, in lumps for roasting in stalls. Colonel Sellers 

 Mine, Leadville, Lake County, Colorado. (51072.) The average composition of this 

 ore is as follows : 



Lead (Pb) 30.53 per cent, (varies from 20 to 40 per cent.) 



Zinc (Zn) 16. 33 per cent, (varies from 12 to 29 per cent. ) 



Iron (Fe) 14.42 per cent. 



Silica (SiOi) 5. 96 per cent. 



Sulphur (S) 29.24 per cent. 



Silver (Ag) 40 ounces per ton (varies from 20 to 60 ounces per ton). 



(2) Galena and blende, with a little chalcopyrite and quartz, iu lumps for roasting 

 installs. Cusihuiriachic Mining Company, Chihuahua, Mexico. (51073.) Atypical 

 analysis of this ore is as follows : 



Lead (Pb) 45. 00 per cent, (varies from 8 to 53 per cent.) 



Zinc (Zn) 11. 83 per cent, (varies from 6 to 16 per cent. ) 



Iron (Fe) 3. 88 per cent. 



Silica (SiO;) 20. 00 per cent. 



Silver ( Ag) HO ounces per ton (varies from 100 to 200 ounces per ton). 



Gold ( Au) 0. 05 ounce per ton (varies from 0.05 to 0.35 ounce per ton) . 



