MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 15 
seemed to indicate that the crystalline limestones and schists of the 
Highlands might be Precambrian in age, and that they were not 
necessarily the highly metamorphosed equivalents of Cambro- 
Ordovician rocks at all. 
During the years 1883 to 1886 the Geological Survey of the State 
of New Jersey 2° undertock a systematic study of the geology of the 
Highlands region within the borders of that state. In the annual 
report for 1883 the facts then known were assembled and summar- 
ized as an introduction to the more extensive and detailed studies 
which were made later by F. J. H. Merrill and N. L. Britton. 
In this report the geographical extent, surface features and rocks 
of the Highlands of New Jersey are rather briefly described, but the 
structure is discussed at some length, the authors referring particu- 
larly to dip, strike, pitch, folds and faults, and mentioning in con- 
nection with the ore, such structures as pinches, shoots, bottom rock 
and cap rock. The authors accept a hydroclastic origin for the 
magnetites, however, as it is stated (p. 35) that “the magnetic 
iron-ore beds partake with the associated gneissic strata of all the 
essential and accidental features or elements belonging to stratified 
rocks. They possess dip, strike and pitch, and are folded, faulted 
and pinched as other rocks about them. Lamination, cleavage and 
jointing are also observed, though much more rarely. Hence, when 
viewed in connection with the associated stratified rocks, the con- 
clusion is unavoidable that they were deposited as sediments and are 
of the same age with them.” 
Britton and Merrill struggled with the complexities of Highlands 
geology for the succeeding two years without adding much to the 
knowledge of it. In the report for 1885 they classified all the 
crystalline rocks of the Highlands area as Archean, but were unable 
to make any further subdivisions. The ores were regarded as of 
sedimentary origin and contemporaneous with the inclosing gneisses. 
In order to explain the presence of hornblende, pyroxene, biotite, 
epidote, apatite and other like minerals in the ore bodies it was 
conceived that ‘“ considerable segregation’ accompanied the meta- 
morphosing processes, with “intense chemical action” during the 
formation of the magnetite. 
Doctor Britton continued the work during the following year, 
and for purposes of classification divided the rocks into (1) a 
massive group, in which he included those massive types with little 
———— 
20 Annual Report of the State Geologist for 1883, p. 27-77. Idem 1884, 
p. 57-60; 1885, p. 36-55; 1886, p. 70-112. 
