210 The American Geologist. October, 1895 
evident. That its existence, whether the ore be hematite (or 
linionite) or magnetite, must be based in some cause equally 
applicable of operating over areas so widely separated at the 
same time, is equally apparent. That it antedated, in part at 
least, the main gabbro disturbance, which closed the Animikie 
portion of the Taconic, is plain, since the gabbro has rendered 
it magnetite where it has been in contact with the gabbro. It 
is with some satisfaction that it can now be stated that work 
recently done for the Minnesota survey by Mr. J. E. Spurr, 
after prolonged investigation into the environments of the iron 
ores of the Mesabi range, has resulted in a substantial demon- 
stration of the oceanic nature of the rock from which the ore 
is produced by metasomatosis and of the probable existence 
of organisms in the cotemporary Taconic ocean as the primal 
source of the ore.* In short, Mr. Spurr's result on this point 
indicates that the iron ores of this geological horizon were at 
tirst in the form of greensand, and that foramini feral remains 
contributed to the unstable chemical condition in which the 
primary glauconite rock was formed. This important discov- 
ery accords with other facts known before which pointed to- 
ward a very early oceanic origin for these ores. It also 
explains their existence at the same stratigraphic plane and 
over a wide extent. 
Chondrodite, a characteristic mineral of the limestones of 
the Taconic in New York and New Jersey, at first supposed 
to be proof of their Archean age, also accompanies the lime- 
stones of this horizon in Canada, | but has not yet been re- 
ported further west. 
Without further specification of the lithological constants 
of the Taconic it may finally be remarked that the usual rock 
kinds, such as sandstone, limestone and graphitic slates,which 
succeed each other in these strata in the east and in Minne- 
sota, when the same are non-crystalline, are quite similar and 
occur in the same successional order, and when crystalline are 
converted into quartzytes, schists and marbles having notice- 
able pectiliarities ; and that, finally, they are accompanied in 
the two regions by almost an identical succession of physical 
disturbances, manifesting cotemporary non-conformities in 
the stratigraphy. 
^Bulletin X, Minnesota Geological Survey, 1894. 
tGeology of Canada, 1863, p. 586. 
