Laurentian Magnetic Iron Ore Deposits. 139 



This formation, with its sulphury ore, occupies the major part of the town- 

 ship Crystalline limestone occurs northwest of Irondale, and the enormous 

 escarpment extending through the central portion of the township to the lake 

 may be due to the rapid erosion of limestone beds. This may never be proven, 

 as the Champlain clays and sands extend a long distance back from the lake, 

 concealing everything from view. One of the most interesting quartz and feld- 

 spar veins I have ever seen occurs in the northern-central portion of this town- 

 ship. Crown Point itself is formed by the Cambrian limestones capped by 

 Champlain clays. 



TICONDEROGA. 



There is very little information on this township in my possession. All I can 

 say at present is, that all the rocks I have seen convince me that the series 

 belong to that of eastern Crown Point and southern Moriah. It abounds in 

 beds of sulphury iron ore and large deposits of crystalline limestone with plum- 

 bago. The rocks are, many of them, thinly bedded quartzites and hornblendic 

 syenites. 



I am indebted to Mr. William H. Case, C. E., of Port Henry, for informa- 

 tion concerning a deposit of crystalline limestone capped by Potsdam sandstone, 

 in the west-central part of the township, near Putnam's pond, lot 179 of 

 Stoughton and McClellan's tract ; also of a glacial moraine in the same 

 vicinity. 



The presence of Potsdam sandstone at this elevated point, and so far from the 

 lakes, would rather indicate that there have been great disturbances since the 

 deposition of this formation. The Cambrian limestones are to be seen at Fort 

 Ticonderoga, and also extend along the lake front. 



Lake George owes its origin to a dam of glacial debris capped by Champlain 

 clays, across the northern end of a valley extending into Warren county. It is 

 possible that the lake is really formed by two valleys — the summit being at the 

 Thousand Islands — the one having its pre-glacial outlet to the north, the other 

 to the south. I am informed the Potsdam sandstone occurs in many places 

 along the lake. 



SCHROON AND MINERVA. 



I am satisfied that the township of Schroon is occupied by the Labradorites 

 and the crystalline limestones with the associated gneisses. 



The limestone occurs along Paradox lake and extends into the township of 

 Crown Point, along the line of the brook which forms the north and the west 

 boundary of the Lower Laurentian rocks of Hammondville. Undoubtedly 

 this crystalline limestone extends southward further than it has yet been traced. 

 It occurs just west of the village of Schroon Lake. In the western portion of 

 the township the rocks have a similar aspect to those in Ticonderoga, and I 

 have reason for classing them with those of that region. At Schroon Lake vil- 

 lage the Chazy limestone occurs with fossils. The outcrops are not extensive, 

 being covered by a sand and clay deposits. The southern portion of Minerva 

 township is occupied principally by the crystalline limestones with the associated 

 gneisses. 



The lower Laurentian makes its appearance in a bold mountain, in the east- 

 central portion of the township. The Rosenkranz mine is located here. The 

 11 Thorn's survey " probably includes nearly all of this uplift. It is flanked on 

 the southeast, south and west by crystalline limestones. As for the western and 

 northern portion of the township, I have no data, but the rocks belong undoubt- 

 edly to the Labradorite and the Limestone series. 



