104 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



from variDiKs miues in tlie ^reat bed ot magnetite iu Berks, Chester, 

 ami Lebanon Conntios, PonnNylvania. 



All of this bed of magnetite carries considerable coi)per, and at times 

 portions carry suihcient to bo Avorked for that metal. The ores consist 

 of magnetite and snlphides of copper, together with decomnositiou 

 products of the latter, including silicates and carbonates. 



Tlie ores are represented by eight specimens. 



(1) Silicate and carbouate of copper, on magnetite. Jones Mine, Berks County, 

 Pennsylvania. (5163.) 



(2) Cbalcopyrite, silicate and carbonate of copper, on magnetite. Jones Mine, Berks 

 County, Pennsylvania. (5154.) 



(3) Cbalcopyrite and malacliite. Jones Mine, Berks County, Pennsylvania. (5175.) 



(4) Clialcopyrite, in rougb crystals, and magnetite. Jones Mine, Berks County, 

 Pennsylvania. (5164.) 



(5) Cbalcopyrite, carbouate of copper, and magnetite. Jones Mine, Berks Couuty 

 Pennsylvania. (5165.) 



(6) Cbalcopyrite. French Creek Mine, Chester County, Pennsylvania. (5167.) 



(7) Cbalcopyrite, pyrite, crystallized, and magnetite, witb a slight coat of carbon- 

 ate of copper. French Creek Mine, Chester County, Pennsylvania. (516L) 



(8) Carbonate of copper, impure. Cornwall Iron Mine, Lebanon County, Pennsyl- 

 vania. (11679.) 



The process at these works is divided into five distinct operations. 



First operation. — The ores are subjected toa roasting fusion, whereby 

 the copper and a considerable amount of the iron, in the form of sul- 

 phides, are concentrated into matte. (31298.) 



The earthy impurities of the ores form a slag sufQciently free from 

 copper to be thrown away. (31209.) 



Second operation. — The first matte is subjected to a roasting fusion, 

 whereby a second matte, called " blue metal," containing more copper, 

 and less iron and sulphur, is obtained. (31301.) 



The slag obtained in this operation contains a considerable percent- 

 age of copper, and is used as a flux in the first operation. (31302.) 



Third operation. — The blue metal is subjected to a roasting fusion, 

 whereby a third matte, called " white metal," containing more copper, 

 and less iron and sulphur, than blue metal, is obtained. (31305.) 



The slag contains a large percentage of copper, and is used as a flux 

 in the second operation. (31303.) 



This operation is further illustrated by two samples of white metal, 

 extra, showing filaments of metallic copper, commonly called " Nigger 

 Wool." (3130G and 31307.) 



Fourth operation. — The white nietal is subjected to a roasting fusion, 

 whereby blister copper is obtained. Blister copper contains only a small 

 amount of impurities. (31309.) 



The slag contains a very large percentage of copper, and is used as a 

 flux in the third operation. (31310.) 



Fifth operation. — The blister copper is first melted and subjected to 

 the oxidizing action of the air, in order to remove the imi)urities as far 

 as possible. This operation introduces a large excess of oxygen into 



