310 The American Geologist. November, ist*7 
ation from a lii^-lily basic aggregate originally constituting 
this (iivision of the Archean schists. This division, there is 
some reason to believe, is near the top of their stratiform de- 
velopment in this region. 
I have referred to the ore deposits at Cranberry as lenses. 
Yet they lack the definition of concrete ore bodies, or at least 
outlines of definite form. They may be more accurately de- 
scribed as lenticular concentrations of magnetite in pj^^roxene 
with their longer axes conformable to the lamination or 
divisional structure of the enclosing schists, and graduating 
into pyroxene more or less epidotic. While rich aggregates 
of magnetite are occasionly met with, the bulk of the ore is 
an admixture of the two minerals along with, though rarely, 
a few accessory minerals like quartz and calc-spar represent- 
ing, together with epidote, derivative ol" residual products of al- 
teration of uni-silicates or silicates, not in atomic combination. 
The separation of magnetite is also incidental to this alter- 
ation, as we may well believe. The breakir.g up of basic ag- 
gregates whether eruptive or clastic into schistose products 
by molecular and physical deformation has come to be com- 
monly described of late as a process of differentiation. These 
are simply new and convenient terms for phenomena long 
since described by Bischof followed by many other writers. 
I have elsewhere described external local separation or 
differentiation of specular oxide of iron from a stratiform 
and probabl}'^ stratified amorphous basic aggregate in the Cle 
Elum valley in the eastern foot hills of the Cascades in Kitti- 
tass county, in the state of Washington. The circumstances 
here point indubitably to molecular alteration incidental to 
weathering action. Several years ago I also published de- 
scriptions of superficial and otherwise local differentiation or 
concentration of specular ferric oxide from basic eruptive 
rocks strictly in circumstances favorable to weathering action. 
T refer to outcropping parts of dykes and more expansive in- 
trusions of basic diorite on the south shore of the island of 
Cuba, in the neighborhood of the very remarkable develop- 
ments of specular iron ores the origin of which I was enabled 
to trace to replacement of emerged and disrupted coral rock.* 
I have also described in previous pages of the Geologist 
numerous other occurrences of the same type on islands of 
*Am. Jour, of Sc. [3] xxviii, 416: Trans. Am. Inst. Min. Eng. xviii, 613. 
