ELIZABETHTOWN AND PORT HENRY QUADRANGLES 1 25 



little magnetite and a stray zircon or two. The rock is much more 

 acidic than the walls within which it is found, but its mineralogical 

 affinities with the acidic phases of the syenite are close. 



It seems inconceivable that a little dike should occur alone, but 

 no other eruptive masses have been detected with which to con- 

 nect it. 



Pegmatites. The ore bodies are occasionally cut by pegmatite 

 dikes of a very coarse character and of interesting mineralogy. 

 They are chiefly quartz and orthoclase, although oligoclase enters 

 also into the aggregate. In the walls of Old Bed pegmatitic de- 

 velopments are characteristic of the edges and limits of the ore 

 body and contain also coarse hornblende and large, coarse crys- 

 talline magnetite. They seem in some way to be associated with it 

 in origin. In the '* 21 " pit streaks of; pegmatite run parallel with 

 the general foliation and again give the impression of having been 

 intimately involved with the ore at the time of formation. AUanite 

 appears at times in these pegmatites and presumably from these or 

 from others somewhere in this pit, Prof. James Hall obtained a 

 superb crystal which was formerly in the collections at Yale Uni- 

 versity [Dana, E. S. On a Crystal of Allanite from Port Henry, 

 N. Y., Am. Jour. Sci. June 1884. p. 479]. 



Ten years or more ago, in mining below the present floor of the 

 "21 " pit a large pegmatite vein or dike or mass was encountered, 

 whose relations to the ore are not accurately known to the vv^riter. 

 Many tons of it were thrown on the dump and it was found to be 

 rich in zircons, at times of rather large size and of great perfection. 

 Much less frequent arsenopyrite also appeared and one specimen 

 of a black coaly mineral, obviously one of those containing the 

 rare earths, but not sharply determined. In this mass of peg- 

 matite allanite strangely enough has not been detected. Magnetites 

 of the familiar lamellar growth, with layers parallel with the 

 octahedron faces, are abundant. 



In the lower workings of the mines on Barton hill pegmatitic 

 bodies of very interesting character have been encountered, some 

 of which are now exposed in the new tunnel, which will further 

 develop these lower lying ores. One mass of white fluorite with 

 magnetite disseminated through it is cut by the tunnel and en- 

 tirely forms one wall for a sufficient distance, to raise the ques- 

 tion of its utilization. In other places in these workings white 

 quartz and disseminated magnetite appear of obvious pegmatitic 

 affinities. On the dumps of the North pit, scapolite enters into 

 other pegmatitic lumps v>diose exact source in the old workings is 



