MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 9 
detailed description of Highland geology appeared in a final report 
of the geology of New Jersey, by Henry D. Rogers,® who was then 
state geologist. 
In that portion of the report dealing with the primary rocks, the 
gneisses are described as folded and metamorphosed sediments, and 
the northeast-southwest ridges are judged to be anticlinal folds. He 
likewise speculated tentatively on the origin of the magnetites, which 
he conceived to have been derived from igneous sources. “ The 
several circumstances here spoken of in the structure of these metal- 
liferous veins, seem strongly to imply that they are real veins of 
injection, and not true beds, contemporaneous with the adjoining 
gneiss, as some have supposed.” (p. 22) 
Rogers further remarks that the gneiss inclosing the magnetite 
bodies was probably steeply dipping before the “intrusion”’ of the 
veins: “for it is inconceivable how a forcible injection of fluid ore 
could enter a series of beds, lying in a horizontal position, without 
in some cases causing and occupying fissures transverse to the 
strike of the strata.” (p. 36) 
He also observed that the ore is confined exclusively to the “ pri- 
mary’ (Precambrian) rocks and correctly concluded that the for- 
mation of the magnetite bodies preceded the deposition of the Paleo- 
zoic strata. 
In 1843 appeared those classic volumes issued by the State of New 
York, entitled “ Natural History of New York.” In part I of this 
series, comprising the “Geology of the First Geological District,” 
Mather,’ under the head of “ Metamorphic rocks,” described: “ such 
rocks of the first geological district as have not yet been described, 
and of which there is demonstrative evidence, or such as renders it 
highly probable, that they were originally sedimentary rocks but 
have since been altered in their character, so as to change them into 
such rocks as have usually been called primary.” (p. 439) 
He did not include in this class granite, gneiss, hornblendic gneiss, 
“sienite,” or the plutonic rocks generally; these he discussed in 
another chapter under the head “ Primitive rocks;” he did include, 
however, “ talcose slate” of Annsville and Gallows Hill (Hudson 
river phyllite) ; “granular quartz rock” (Poughquag quartzite), and 
the crystalline limestones of Putnam, Westchester, New York, Rock- 
land, and Orange counties, and concluded that the crystalline lime- 
6 Rogers, Henry D. Final Report on the Geology of the State of New 
Jersey, p. 12-43. 1840. 
7 Mather, W. W. Geology of the First Geological District, Natural History 
of New York, 1843. 
