MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 125 
Percent 
PROSE seh Bik Be Sige NOREEN URES UCM SHSM Mb PS Se Ceo ace ON a 54.225 
Nan SatlOusMoxe Lemna etme yume tn ny ln nice inn 0.186 
HANI NENA OUB SREY I NC Eilean rey HIS RUE DEMAND Lee aN AO 0 on TLU NA 3.078 
IO RTE ay SEONG. OL COT ALE SHER OMRON ROTC COUT SRR RE OMRON To aa 1.450 
INIA OTIES TAO roe aloe SA Se Ne agate aire NES 10.065 
Mita tin! ORT w yy LAN. MEE PREC ESL hs Pye ge trace 
Caron dioxide pony Mei RE LN uM yea aN Al 0.251 
PHOSPHONUS em vero tatocts a rlalaba ebay sept ciaceua alert elans 0.012 
SHU BTC Ae Ai eal At ALL ee 8.780 
Kilworinemrancdimalleallieswmy tas ele tant sieve cialie 2) 0.427 
INIOISEUT EME ae i era ames Ue Narasienstanel alci arena) Galas ens po titel 0.048 
Combined nwater i Miy. sees Pe Oe OO! SE 0.758 
Semi ba ay a ie AIS HR a ER Aa PRR 0.014 
This is a remarkable composition; according to Wendt (op. cit.) 
the ore was absolutely self-fluxing, the only additional material 
which was necessary to add to the burden of the furnace being a 
little lime, in order to flux the ash in the fuel. 
Not only does the ore in the Mahopac mine bear a striking 
resemblance to that in the Tilly Foster in chemical composition ; the 
petrographic resemblance is equally as striking. 
Samples of material from the old dump carry chondrodite, 
clinohumite, clinochlore, phlogopitic colorless mica, carbonate, 
serpentine and magnetite in end-stage relations cutting, corroding 
and replacing all the other minerals (see plate 9, figure 1). 
Like the Tilly Foster, the ore is clearly the result of the replace- 
ment by magmatic end-stage processes of an interbedded limestone 
in the Pochuck-Grenville. 
Coarse white granite (Pochuck granite) outcrops a little to the 
southeast of the old boiler house; the strike here is approximately 
north 57° east. Several hundred feet to the east and near the road, 
an outcrop of granitized Pochuck-Grenville strikes north 63° east, 
and dips 35° southeast. East of the Kent Cliff road, just at the 
edge of the western margin of the little valley which is occupied by 
the little creek that flows into Kirk lake the strike shifts to north 
25° east, and the dip has steepened to 90° ; and about one-fourth of 
a mile north, on the west side of the road, an outcrop of Pochuck- 
Grenville dips toward the northwest at a low angle, thus giving the 
impression that here likewise an obscure inherited fold controls in 
part the attitude of the ore body. 
Although no limestone can be found in the immediate vicinity of 
the mine, and notwithstanding the fact that the walls of the ore 
body are Pochuck-Grenville, more or less modified, the presence of 
the peculiar and typical contact minerals previously enumerated, 
