106 P.TTLLETIN 42, UNITED STATES NATIONAL MUSEUM. 



of solid ore, most of it, however, being secoiul class or concentrating 

 ore. Within tlie vein are fre(iuently found chutes of rich ore, irregu- 

 hirly distributed. Large bodies of nearly' pure chalcocite were found 

 in some of the mines, especially the Anaconda. 



The ores of the region may be divided into three classes. First, ship- 

 ping ore, consisting of high grade chalcocite ore, carrying 50 per cent, 

 of co])per, which is shipped away for smelting. Second, smelting ore 

 carrying about 30 per cent, of copper, which is smelted on the spot. 

 Third, concentrating ore, carrying from 10 to 20 per cent, of copper, 

 which is first roughly concentrated and then smelted. Owing to the 

 cost of labor and the lack of local consumption, the smelting is con- 

 fined to a single operation for the production of a high grade matte. 



MONTANA SMELTKR. 



These works treat the ore from several of the mines, but especially 

 the Colusa, which carries most of its copper in the form of chalcocite. 

 Besides chalcocite the ore contains considerable pyrite and a little 

 bornite. Solid lumps of the rich sulphide generally contain native 

 silver in very thin plates. The rich ores are shipped away directly, 

 the second quality are treated for the production of matte in a rever- 

 beratory furnace, while still poorer ores are concentrated by jigging, 

 and then treated for matte. 



Ore. 



(1) Chalcocite, containing a little pyrite and sbovring small flakes of free silver. 

 Shipping ore. (55639.) 



(2) Chalcocite, bornite, pyrite, and quartz. Concentrating ore. (.55629.) 

 {'.i) Crashed ore. (5562-<.) 



(4) Coarse concentrates, containing a great deal of chalcocite and being very 

 rich in copper. (55626.) 



(5) Medium concentrates, containing some pyrite and quartz. (.').")625. ) 



(6) Fine concentrates, containing considerable pyrite and quartz. (55624.) 



(7) Tailings, consisting largely of quartz. (55623.) 



Flux. 



(1) Limestone. (.5.5636.) 



(2) Iron ore. (.55634.) 



Fuel 



(1) Bituminous coal, from Bozeman, Montana. (5563S.) 



(2) Bituminous coal, from Pleasant Valley, Utah. (55637.) 



Final jyroducta. 



(1) Matte, containing 65 per cent, of copper and 55 to 60 ounces of silver per ton, 

 (.5.5616.) 



(2) Slag, produced in smelting matte. (.55618.) 



Accesmrien. 



(1) Quartz, used for making furnace bottoms. (55635.) 



(2) Blister copper, from old blast-furnace snielting. (55633.) 



(3) Slag, from old blast furnace smelting. (55622.) 



