O NEW YORK STATE MUSEUM 



magnetites, (2) titaniferous magnetites, and (3) hematites. Of 

 the three classes the nontitaniferous magnetites are the character- 

 istic product of the region and have afforded by far the. greater 

 part of the output. 



The occurrence of limonite deserves some notice, perhaps, 

 though it can hardly be considered as an available resource at the 

 present time. It is limited to surficial accumulations of impure 

 bog ore doubtless derived from solution by ground water of the iron 

 minerals that accompany the crystalline rocks. The ore is only 

 occasionally found in deposits of any size and is then usually too 

 lean to be marketable. It has been exploited on a small scale at 

 times when conditions were specially favorable. 



The two kinds of magnetites mentioned form the basis of the 

 present report. They are quite distinct in respect to commercial 

 considerations, as well as in the particulars of their geological 

 associations and local distribution, wherefore it has been thought 

 advisable for purposes of description to place them in separate 

 divisions. 



The hematite ores are practically confined to a single district 

 on the west side of the Adirondacks. They have been mined for 

 over 50 years and still supply a considerable output. They occur 

 within metamorphosed Precambric sediments, mainly quartzose 

 schists and limestones, where they have been formed by a process 

 of chemical replacement. Their detailed description is reserved 

 for a future paper. An isolated deposit of hematite, the only 

 one that has been worked outside of the western district, is found 

 near Fort Ticonderoga, on Lake Champlain, the particulars of 

 which are given on a subsequent page of the present report. 



The magnetite deposits of the Adirondacks have furnished alto- 

 gether not less than 35,000,000 tons of commercial ore, an output 

 that ranks them among the more important sources of this class 

 of ores in the country. They have been exploited almost con- 

 tinuously for the past century, the earliest operations in the Cham- 

 plain valley dating back to about 1800. Though some deposits 

 have been practically exhausted by past operations, these are 

 mostly the smaller ones, many of which would not repay working 

 under existing circumstances. The larger mines now operated 

 can continue along present lines for an indefinite period, so far 

 as it is possible to judge their ore reserves. 



A diminished ore supply, in fact, is of less concern for the future 



ess of mining, than the possible recurrence of a period of 



inactive demand for the ores such as has been felt at different 



times during the past. It is believed, however, that the industry 



