34 NEW YORK STATE MUSEUM 



port. In the Old Bed workings at Mineville, the ore is removed 

 in large chambers which are extended downward with the progress 

 of operations, as the main mass of ore lies nearly vertical. The 

 chambers are of great size, measuring 200 feet or more from roof 

 to floor. Timbering or other artificial support is not required in 

 the Adirondack mines, and little trouble has been experienced 

 from caving. The workings are relatively dry, as the wall rocks 

 are nearly impervious to water. 



Concentration of the magnetites has been practised since the 

 early days of mining in the region. As early as 1836, according 

 to local records, a plant was in operation at Palmer hill for treat- 

 ing the ore by a magnetic process. The details of this installation, 

 an interesting precursor of the modern plants, have unfortunately 

 been lost, though it is hardly probable that the venture could have 

 been successful. A wet gravity system of concentration was com- 

 monly used up to about 15 years ago when the magnetic process 

 was perfected to an extent that made its introduction feasible. 

 This process is now generally recognized to be well adapted to the 

 Adirondack magnetites. 



At present there are six concentrating plants in the region; two 

 are installed at Mineville, two at Lyon Mountain and one each at 

 Arnold hill and Benson Mines. Another plant is in course of 

 erection at the Cheever mine near Port Henry. In 1906 the mills 

 at Mineville, Lyon Mountain and Arnold hill, which were the only 

 ones operated, crushed 729,091 long tons of ore, making 479,644 

 long tons of concentrates. 



The system of magnetic concentration employed is practically 

 the same at all the mines. It involves dry crushing, sizing and 

 treatment of the product by magnetic separators of which the 

 Ball-Norton drum type is the one commonly used. 1 The crush- 

 ing is regulated as to fineness by the granularity of the ores which 

 varies at the different mines. As a rule it is not carried to the 

 point where the greatest saving of the magnetite would be effected, 

 since the production of fine concentrates is not desirable from a 

 metallurgical standpoint. 



The difficulty in handling the finer grades of concentrates in the 

 blast furnace has been something of a drawback to the success of 

 magnetic concentration as applied to ores in which the magnetite 

 is intimately intergrown with the gangue minerals, an association 

 that is not uncommon in the Adirondacks. Briquetting has not 



1 For further details of the apparatus and methods used, consult the issues 

 of the Engineering and Mining Journal, for June 9, and November 17, 1906, 

 wherein are described the mills at Mineville and Lyon Mountain. 





