530 NEW TOKK STATE MUSEUM 



boundaries of the several iron-ore districts, and is, as it were, an 

 iron mines map. The geology of a county or district gives the 

 clue in searching for ore; and its importance can not be too 

 strongly stated, both as a guide, suggesting exploration, and 

 warning against unnecessary and fruitless surveys and wasteful 

 outlays of time and money. Thus, for example, the magnetites 

 belong in the crystalline rock districts, and the search for them 

 in the later, sedimentary rocks of the adjacent territory would be a 

 hopeless task; or, again, the exploration of the Highlands or 

 Adirondacks, for carbonate ores, would be equally unscientific and 

 destitute of good results. 



The geological formations, which are characterized as definite 

 Ore horizons, become the basis of a natural arrangement of the 

 ore districts of the State. They are well marked geographically 

 also. 



Following this geologico-geographical arrangement, the groups 

 and iron-ore districts are : 



I. The Highlands of the Hudson. — Magnetic Iron Ores. 

 II. The Adirondack Region, Including the Lake Champlain 

 Mine. — Magnetic Iron Ores. 



III. The Hematites of Jefferson and St. Lawrence Counties. 



IV. The Clinton or Fossil Ores. 



V. The Limonites of Dutchess and Columbia Counties. 

 YI. The Limonites of Staten Island. 

 YII. The Carbonate Ores of the Hudson River. 



A few isolated mines can not be thus classified, as the hematite 

 near Canterbury, Orange county, Ackerman's mine near Union- 

 ville, "Westchester county, the N apanock and Wawarsing mines, 

 in Ulster county, the hematite of Mt Defiance in Ticon- 

 deroga, and the bog iron ores, which are scattered in all of the 

 great divisions of the State. The iron sands of the shores of 

 Long Island are left out, as not properly a natural source of 

 iron. 



I. The Highlands of the Hudson. — Magnetic Iron Ores. 



Magnetite is one of the common minerals in the crystalline 

 rock region of the Highlands. It occurs as an accessory con- 

 stituent in the granitic and gneissic strata ; and by itself, forms 



