ADIRONDACK MAGNETIC IRON ORES 143 



The immediate area about the mine is occupied by the Adiron- 

 dack Precambrics. These rocks extend southward as a belt of 

 gradually diminishing width to within 4 miles of Little Falls, pass- 

 ing at the borders beneath the Lower Siluric strata (Beekmantown, 

 Trenton and Lorraine) which spread over the region to the south. 

 There is a large outlier of Precambric syenite at Little Falls and 

 smaller ones of the same rock at Middle ville, northwest of Little 

 Falls, and at a point about half way between the latter locality 

 and the southern end of the main area. The contact between the 

 Precambric and Paleozoic strata on the east side of the belt is 

 marked by a heavy fault which begins south of the Mohawk river 

 and runs northeast passing about 2 miles east of the mine. 



The principal representative of the Precambric rocks is syenite, 

 a greenish augite-bearing variety that is identical mineralogically 

 with the great syenite masses in the central Adirondacks. It has 

 a gneissoid appearance in most cases and shows strong crushing 

 effects in the granulation of the feldspar. Occasionally uncrushed 

 remnants of feldspar may be observed surrounded by granular 

 material, like an augen gneiss. The syenite is exposed over most 

 of the area north of Salisbury Center. 



The Grenville series of gneisses and schists form the southern 

 extension of the Precambric belt south of Salisbury Center and is 

 exposed north of the mine in two areas which are bordered by the 

 syenite. It consists of light colored quartzose gneisses interbanded 

 with darker hornblendic or micaceous varieties. Crystalline lime- 

 stone, usually a prominent member of the series, apparently has a 

 very limited development within the area ; the only outcrop that has 

 been recorded is one observed by the writer at a point a little 

 north of Salisbury Center. The gneisses are believed by Cushing 

 to represent original sandstones and shales. 



A reddish gneiss comprised mainly of quartz and alkali feldspar 

 occurs at a few places in association with the syenite and rocks of 

 the Grenville series. Its field relations as well as its composition 

 suggest an original granite that is probably intrusive in the sedi- 

 mentary gneisses. Cushing mentions also the occurrence of black 

 gneisses, containing hornblende and biotite and occasionally 

 pyroxene, and gray gneisses of granitic composition which are 

 regarded as igneous derivatives. 



Ore bodies. The deposit which has been principally worked 

 extends nearly east and west along the highway 2\ miles north of 

 Salisbury Center. It consists of an elongated zone made up of 

 magnetite in one or more bands intercalated between layers of 



