100 NEW YORK STATE MUSEUM 



4 As more or less distinct crystals (dodecahedral), without 

 hornblende rims, in a certain special basic syenitelike or acidic 

 dioritelike rock. 



In case number i (for example, Parker and Sanders Brothers 

 mines) the garnets have, in the usual manner, crystallized out of 

 masses of sediments under conditions of thermal and dynamic 

 metamorphism. These garnets are rarely as much as an inch 

 across and their origin presents no problem of special interest. 



In case number 2 the garnets appear mostly to have crystal- 

 lized out of the original magmas, their formation possibly having 

 been due to some assimilation of granville sediment by the syen- 

 ite or granite. The facts that these garnets occur so sporadi- 

 cally and that actual examples of local assimilation have been ob- 

 served in the region strongly favor this view. Since these ga.^- 

 nets seldom attain a diameter of an inch and are so scattered, 

 no attempt has ever been made to mine them. Sometimes, as in 

 the gabbros, the garnets have often been produced secondarily, or 

 after the cooling of the magma, because they commonly form re- 

 action rims around other minerals. 



Case number 3 (for example, Rogers, Oven mountain, and 

 Rexford mines) is of particular interest because of the very large 

 garnets surrounded by the reaction rims of hornblende. 



Kemp and Newland^ have briefly described a garnet deposit 

 (formerly worked by the Messrs Hooper) just across the line in 

 Essex county less than a mile west of the village of North River 

 and four and one-half miles north of the Rogers mine. As judged 

 by their description the type of occurrence appears to be similar 

 to that in the Rogers, Oven mountain, and Rexford mines, though 

 no mention of the hornblende rims is made. In conclusion they say : 

 The origin of this peculiar bed presents an interesting theme. The 

 country rock is probably igneous. Its mineralogy and structure favor this 

 derivation. The garnet rock must be either an altered form of a very impure 

 limestone, or else a very basic igneous rock that was an original sheet or 

 dike. The former supposition appeals more strongly to us. 



Later Newland^ says of the garnet deposits in general that : 

 The garnet is usually associated with a basic hornblende rock or 

 amphibolitc which forms bands and lenses in the more acid gneiss that 

 constitutes the country rock. 



In his brief description of the more recently worked garnet 

 deposit of northern Essex county he speaks of the '' amphibolite 

 bands, which have been caught up during the intrusion of the 



1 17th An. ReD. X. Y. State Geo!., 1897, pages 548-49- 



2 N. Y. State Mus. Bui. 102, page 71. 



