174 The American Geologist. 'ic\,i^m\wx,\m: 
of this ore are found sometimes irregular masses of rock like No. 
?i. as if remnants of that stratum not yet converted to ore, while 
some strata of soft ore are found also in the midst of No. 8. 
Not enough working has been done yet to reveal all the relations 
of the ore to No. :}. 
5. Pewabic quartzyte. In the near vicinity of the gahbro foci 
this is remarkably modified. Originally probably a chemical 
oceanic precipitate in its upper portion it is consolidated to a vit- 
reous quartzyte, but at more distant points it is composed of dis- 
tinct rounded grains. The upper portion is in the form of chal- 
cedonic silica (so-called), a phase which extends westward, with 
modifications, so far as observed, at least to town 60-13. On 
the other hand this quartzyte becomes less siliceous, having a 
feldspathic element, and even an olivinitic constituent, and some- 
times large hornblende crystals embrace the quartz grains in a 
common matrix. When olivinitic it is also magnetitic and con- 
stitutes an important iron ore. In some places farther west, near 
the Mississippi river, is a quartz3'te which is evidently the same, 
regularly interbedded with magnetite in thin alternations. 
(). Conglomerate. This is simply the base of the quartzyte. 
and takes on the character of the older underlying rock. When 
it lies on the greenstones its cementing matrix is green, when on 
the granite it is moi'c siliceous and lighter. 
Northward from the strike of these strata extends the Archaean 
complex, embracing the rocks and ores of the Vermilion range 
and the foregoing beds lie unconformably on the upturned 
edges of the older rocks where the two formations come into 
contact. But, wherever the highland spurs of the older rocks 
extend further southward, the primordial strata sweep about 
their bases, dipping in opposite directions on opposite sides 
of the spurs. They occupy no constant level, which might be 
considered an oceanic shore line, but they seem to exist where 
erosive agents have not been able to remove them. Hence they 
may have extended formerly much further north. It happens, 
however, that a range of granitic hills, the Giant's range, occurs 
but a short distance to the north, and sometimes the strike of the 
Taconic is coincident for some miles with the southern base of 
this range. In other places a belt of "greenstone," which, how- 
ever, is itself rather rough and rises nearly as high as the granite 
hills, intervenes ]>etween the Taconic and the granite. 
It is evident that the present surface contour is but a poor 
