MINERAL RESOURCES OF THE STATE OF NEW YORK IO5 



3 St Lawrence and Jefferson counties. Hematite associated 

 with Grenville limestone and schist, as replacement bodies. 



4 Central and western New York. Fossil and oolitic hematite, 

 interstratified with Clinton limestones and shales in horizontal beds. 



5 Dutchess and Columbia counties. Limonite associated with 

 crystalline limestones, slates and schists, representing metamor- 

 phosed sediments of early Paleozoic age. Siderite, or carbonate 

 of iron, accompanies the limonite in many places and in one or two 

 of the mines is the principal ore. The deposits are secondary or of 

 later age than the inclosing rock. 



6 Staten island. Limonite in residual accumulations resting on 

 serpentine. 



I Adirondack Region 



The principal magnetite deposits low in titanium are found on 

 the borders of the Adirondack highland, in Washington, Warren, 

 Essex, Clinton, Franklin and St Lawrence counties, in the eastern, 

 northern and northwestern sections. On the southern and western 

 sides there are few bodies and these have yielded little ore. 



The country rocks are varied in character but in the greater 

 number of occurrences they consist of a light colored massive or 

 gneissic rock which corresponds to granite or syenite in mineral 

 composition. The feldspar is usually an intergrowth of potash 

 (microcline) and soda (albite) varieties, and is associated with 

 moderate to small amounts of quartz. The dark minerals are repre- 

 sented by diopside and hornblende, usually in small amounts. The 

 textures and general habits of the gneisses are frequently those of 

 igneous rocks. In St Lawrence county, however, the magnetites 

 are found in banded rusty gneisses containing more or less silli- 

 manite, closely allied vvdth Grenville rocks to which they may belong. 

 They may have limestone on one of the walls. It seems probable 

 therefore there are at least two classes of deposits — the one charac- 

 terized by their occurrence within the body of igneous rocks and 

 regarded as original segregations within the magma; and the other 

 associated with gneisses and schists which are doubtless old sedi- 

 ments. Of the latter class the derivation of the deposits is uncertain, 

 as they may be held to be contemporaneous with the wall rocks or 

 later migrations into their present sun-oundings, superinduced per- 

 haps by the agency of neighboring igneous invasions. The occur- 

 rence of secondary garnet, hornblende and pyrite is characteristic 

 of this class of magnetites. 



In shape the magnetite deposits vary greatly; they are commonly 

 described as veins, lenses, pods etc., according to the particular 



