MINERAL RESOURCES OF THE STATE OF NEW YORK 1 33 



x\ccording to Smock, who visited many of the mine locaHties 

 when operations were in progress and thus had advantages for 

 observation not now obtainable, the ore occurs in limestones or 

 along the contact of limestone and schist, or it lies wholly within 

 the latter; as a rule the contact affords the most favorable locus 

 for the ore occurrence. The limonite occurs in small irregular 

 pockets as well as large bodies and is accompanied by ochreous clay. 



Some carbonate is found in the workings, intermixed with the 

 limonite or forming independent bodies or horses within the latter. 

 It is the principal ore in one or two of the mines, notably in the 

 Morgan, south of Halstead station, Columbia county, and can be 

 seen in large bodies in the Amenia mine although here the ore is 

 mostly limonite. The carbonate often has a brownish coating of 

 oxide, so that its existence may not be inferred at first glance. It 

 has been suggested by several writers that the carbonate constitutes 

 the original ore from which the limonite has been derived by oxidation 

 and hydration under surface conditions; this view is probably correct 

 in the main, although it is not unlikely that some of the limonite 

 has been formed directly by the weathering of pyrite that occurs 

 rather freely in the schists. There is some question about the 

 method of accumulation of the carbonate; Dana and others have 

 considered the siderite to lie in interbedded seams with the limestone 

 and schists, which if true would mean that the deposits are continuous 

 with the wall rocks; on the other hand, the explanation that the 

 iron has been introduced in solution and as a replacement of the 

 limestone seems more in conformity with the present known facts 

 of the field occurrence. 



The more important mines of the district lie within or close to the 

 limestone valley that borders the high ridges of the Berkshires on 

 the west and extends north and south along the New York and 

 Massachusetts-Connecticut state line. The valley is narrow and 

 broken in places by minor ridges of schist which rise on the west 

 side into a series of prominences somewhat less rugged than those 

 on the east side. This valley is followed by the Harlem Railroad 

 (New York Central lines) and most of the mines are close by. The 

 list of the larger productive properties includes the Dover, Amenia, 

 Manhattan, Maltby, Mt Riga, Dakin and Kelly mines in Dutchess 

 county and farther north the Morgan, Reynolds, Weed, Copake, 

 Hillsdale, Mitchell and Haight mines in Colimibia county. In 

 the Fishkill-Clove valley are the Shenandoah, Sylvan Lake, Pawling, 

 Beekman and Clove mines, all in Dutchess coiuity. 



