TITANIPEROUS IRON ORES OF THE ADIRONDACKS. 15 



The next paper, read by the author, was entitled : 



TITANIFEROUS IRON ORES OF THE ADIRONDACKS 

 BY J. F. KEMP 



\_ Abstract] 



The paper opened with a brief statement of the characters of the two kinds of 

 iron ores which are afforded by the region. The merchantable magnetites, both 

 Bessemer and non-Bessemer, occur in a series of gneisses which surround the great 

 central norian mass and its outlying ridges. The ore-bodies are lenticular or pod- 

 shaped in the smaller examples and conform to the usual type, but the larger ones 

 are quite irregular in shape, and may even form apparent beds several miles on 

 the outcrop. 



The titaniferous ore-bodies may be grouped in two classes ; the one, in basic 

 gabbros, affords low-grade ores, high in titanic oxide and alumina ; the other, in 

 pure feldspathic anorthosites, yields richer ores, which are, however, high in titanic 

 oxide. Ore-bodies of the first class have such geologic relations that they are best 

 explained as basic developments of a gabbro magma. The Split Rock mine, near 

 Westport, is the best illustration and is easily accessible. The second class is almost 

 limited to the vicinity of lake Henderson and lake Sanford, in the heart of the 

 central norian area. The wall-rock is massive, unbrecciated anorthosite, and is 

 almost entirely formed of large, blueish black crystals of labradorite, which lack the 

 crushed borders that give the "mortar structure" to most of the Adirondack 

 anorthosites. 



The ore-bodies are enormous, and by means of the dipping compass one series 

 that crosses lake Sanford has been traced as much as two miles, with a width for 

 the area showing attraction of several hundred feet. Trenches or costeaning pits 

 dug many years ago exhibited ore and anorthosite in streaks. 



The massive ore contains great numbers of labradorite crystals even up to 20 

 centimeters in diameter of a dark green color from innumerable inclusions of small 

 pyroxenes. Each included feldspar is surrounded by a " reaction rim " from 5 to 10 

 millimeters across, consisting of brown hornblende and biotite. From the nature 

 of these included labradorite crystals and the lack of evidence of dynamic meta- 

 morphism in the wall-rock, the argument was made that the ores are segregations 

 from an igneous magma formed during the process of cooling and crystallization. 



In conclusion, a few notes were given regarding recent successful experiments in 

 smelting them and on the peculiar excellence of the resulting iron. 



In discussion, C. E. Van Hise mentioned the similar bodies of titaniferous ores 

 in the gabbros of lake Superior, adding, however, that there had been some infiltra- 

 tion of iron oxide since their formation. 



The paper was discussed by C. R. Van Hise and the President. 

 The following paper closed the list : 



DECOMPOSITION OF ROCKS IN BRAZIL 

 BY JOHN C. BRANNER 



The paper was discussed by I. C. Russell, C. R. Van Hise, H. T. Fuller 

 and the President. It is printed in full in this volume. 



