ADIRONDACK MAGNETIC IRON ORES 41 



The Grenville has been broken up into patches and larger irregu- 

 lar areas by granite which has invaded the series from below. 

 The granite is more or less gneissoid, but yet has a quite massive 

 appearance in contrast with the sedimentary gneisses. It con- 

 sists mainly of microcline and quartz, with biotite and magnetite 

 as the principal dark minerals. It is of pinkish color. The granite 

 frequently cuts across the stratification of the sediments and sends 

 off dikes and stringers which penetrate the latter in all directions. 

 It is very likely a part of the same mass described as being intrusive 

 in the Grenville around Hammondville to which it is very similar 

 in its characters. 



Vineyard and Butler mines. These mines are located on the 

 same deposit. They lie in the narrow valley between Buck moun- 

 tain and the next ridge to the west known as Dibble mountain, 

 just over the border of Crown Point in Ticonderoga township. 

 Their outcrop is 2 miles distant from and 500 feet above Lake 

 Champlain. 



The Vineyard mine was last worked by the Lake Champlain 

 Ore & Transportation Co., during the years 1887 and 1888, but it 

 had been under operation 40 years before. Some of the ore was 

 used at the Crown Point furnace. The deposit can be traced along 

 the outcrop for 100 rods or more following the highway that leads 

 to Crown Point Center. It is inclosed by a laminated black horn- 

 blendic gneiss. The strike for most of the distance is a little west 

 of north, but on the south end it bends around and becomes east of 

 north. The main workings are on the southern portion and con- 

 sist of open cuts and shallow pits sunk on the dip which is westerly 

 at an angle of 40 or more as measured near the surface. The 

 principal pit has recently been pumped out. It is less than 100 

 feet deep and shows 5 feet of ore at the surface which widens to 

 nearly 15 feet at the bottom. 



The ore is a fairly rich, coarse magnetite. It contains pyrite in 

 variable amount, more abundant toward the walls than in the 

 central part. The following analysis by J. B. Britton is quoted 

 from Maynard who states that it was made from a sample after 

 rejecting the most sulfury portion. 



Iron 51.34 



Silica 21.07 



Sulfur 1 . 1 7 



Phosphorus 36 



Water 24 



