ELIZABETHTOWN AND PORT HENRY QUADRANGLES 1 29 



in one dimension at least over half a mile. This is certainly on 

 the face of it suggestive of sedimentary stratification, but in fair- 

 ness we might say that it could also be derived from a persistent, 

 differentiated layer in an igneous magma. It is of itself scarcely 

 conclusive on either side. 



Another feature is the podlike distribution of the ore, affording 

 its swells and pinches, and its tendency to a shinglelike distribution 

 of the larger ore bodies. This structure is most pronounced in 

 the Barton Hill group and is less evident in the Old Bed series 

 which, as thus far developed, are more like one enormous folded 

 pod. As long ago as 1881, the relationships of ore and lighter 

 minerals in the tailings of mills, which were engaged in concen- 

 trating iron ores by wet processes, impressed H. S. Munroe- as 

 imitating the lenticular shape very clearly and the same relationship 

 has been noted by others since. The concentrated black or mag- 

 netite sands, which we not infrequently observe on beaches and 

 along rivers draining areas of magnetite-bearing rocks, are likewise 

 suggestive. They have given much support to the sedimentary 

 view, and it is not so clear that heavy layers of eruptive origin 

 would assume these forms, unless compressed strongly while still 

 viscous. It must be admitted that while not perhaps conclusive, 

 yet the lenticular shape does accord best with sedimentary depo- 

 sition. 



Another consideration, which must be emphasized in the inter- 

 pretation of the rocks, concerns their mineralogy and their paral- 

 lelism with other known cases. There is no doubt that the most 

 abundant rock in the cores has exactly the mineralogy and the 

 texture of the syenites as elsewhere identified. H. P. Gushing has 

 shown these syenites to be beyond question intrusive in their nature. 

 They contain fragments of the Grenville series, undoubtedly 

 caught up in a molten mass. They present irruptive contacts with 

 the anorthosites, penetrating the latter in dikes and tongues. Their 

 mineralogy is essentially that of the eruptive rocks, the augite and 

 l;ypersthene especially being foreign to the metamorphosed sedi- 

 ments. While the ores are often intimately associated, especially 

 with the very acidic phase, described above, and while both these 

 varieties differ from the normal syenite, yet they are so involved 

 with it, that it is quite impossible to believe that they are sedi- 

 mentary and the syenite eruptive. They all hang together in one 

 essential whole or entity and it is almost impossible to regard one 



^School of A/[ines Quarterly. i88t. 3:43. 



