272 F. D. Adams — New Nepheline Rock. 



thing foreign to the original magma and that it merely exists in 

 the rock in the form of inclusions, in calculating out the mineral 

 composition of the rock the calcite is set aside and the primary 

 magma regarded as having the composition of the calcite-free 

 rock. The nepheline syenite of the island of Alno,* it may be 

 mentioned, is characterized by the presence of calcite which is 

 not of secondary origin, whose mode of occurrence in many 

 respects is very similar to that of the calcite found in the 

 nepheline syenite of Ontario. 



Seven typical varieties of the rock have been analyzed and 

 these serve to show the range in composition displayed by the 

 magma. Of these, three were found to belong to the class of 

 the Persalanes and to the sub-class Pesalone ; using the nomen- 

 clature recently proposed by Messrs. Cross, Iddings, Pirsson 

 and Washington, f while three others belong to the class Dosa- 

 lane and the sub-class Dosalone. One is a Phlegrose, one a 

 Vulturose and one a Miaskose, while two are referable to 

 Essexose and one is a Kallerudose. These will be fully 

 described in the forthcoming Report to which reference has 

 already been made. 



In addition to these there is the rock described in the pres- 

 ent paper. This is a variety of the nepheline syenite which 

 is almost free from feldspar and which consists essentially of 

 nepheline and the iron-magnesia constituent, in this case horn- 

 blende. It occurs in the township of Monmouth, about 25 

 miles west of the township of Dungannon. Here, on lots 9, 

 10, 11 and 12 of ranges YII to VIII, a mass of nepheline 

 syenite breaks up through a great band of crystalline lime- 

 stone. The southern limit of this mass is unfortunately mantled 

 by drift, so that its extension in this direction is somewhat 

 uncertain. It has, however, the form of a flattened ellipse, the 

 longer diameter measuring one mile and the shorter diameter 

 about half a mile, and is completely surrounded by the lime- 

 stone. The mass holds many inclusions of the limestone through 

 whose shattered mass it penetrates. These included limestones 

 frequently are coarsely crystalline and are more or less impure 

 from the presence of secondary silicates developed by the con- 

 tact action. These masses have the appearance of being in pro- 

 cess of replacement by the intruded magma. The nepheline 

 syenite in some places along its contact with the limestone is 

 rich in hornblende, but elsewhere along the border it contains 

 but a very small proportion of the dark constituent, so that no 

 distinct endomorphic action can be traced to the influence of 

 limestone. In some few places, however, near the limestone 



* Hogbom, A. G. : Ueber das Nephelinsyenitgebiet auf der Insel Alno. 

 Geol. Foren. i. Stockholm Forh., Haft. 2, 1895, p. 140. 



f Quantitative Classification of Igneous Rocks, University of Chicago Press, 

 Chicago, 1903. 



