28 NEW YORK STATE MUSEUM 



groups, with local variations ranging through both. Its intrusive 

 nature is evidenced by the penetration and absorption of an older 

 formation, a hornblende schist which occupies limited belts in the 

 vicinity, as well as by its pegmatitic and thoroughly massive phases. 



The numerous deposits centering around Arnold hill and Palmer 

 hill, in southern Clinton county, are inclosed by the same Saranac 

 series. The Palmer hill ore body is particularly interesting, in that 

 it consists of a magnetite band in a massive augite-biotite granite 

 that carries fluorspar. This mineral forms an integral part of the 

 ground mass, where it is associated with quartz and feldspar 

 (microcline and orthoclase) reaching at times large proportions. 

 Its presence can hardly be explained except by pneumatolytic 

 action during the consolidation of the rock from a molten state. 

 Fluorspar is a quite common mineral in the magnetites elsewhere, 

 but usually in small quantities and limited, so far as observed, to 

 pegmatite or vein material. 



Syenite of the characteristic Adirondack type is represented in 

 force in the Mineville group of mines. It has been shown by recent 

 drilling to underlie the ore bodies in what seems to be a continuous 

 mass. The rock is of greenish cast and is normally composed of 

 •microperthite, green augite, hornblende and magnetite, but 

 through the addition of quartz and shrinkage of the ferromag- 

 nesian constituents, passes into a lighter reddish rock that is much 

 like the varieties above described. This rock called the " 21 " 

 gneiss in the earlier report of Professor Kemp, forms the hanging 

 wall of the Old Bed group. Its relations to the underlying syenite, 

 as well as the apparent differentiation of the latter into a dioritic 

 phase, are brought out in the article by Professor Kemp included 

 herewith. 



A basic variety of augite-syenite constitutes the wall rock at the 

 mine near Salisbury, Herkimer co., being a part of the intrusives 

 in that region which reach southward from the Adirondacks into 

 the Mohawk valley. The dark minerals (augite, hornblende and 

 magnetite) constitute about 75 per cent of the rock in immediate 

 contact with the Ore, but away from the latter there is a gradual 

 change into the normal syenite. 



While the rocks from the different mine localities have not been 

 chemically analyzed, the following tabulation of analyses taken 

 from a recent report by H. P. Cushing 1 may be useful in showing 

 the general range of the igneous series. The description of the 



1 Geology of the Long Lake Quadrangle. N. Y. State Mus. Bui. 115. 1907. 

 p. 5«o- 



