350 he. Pumpelly—Paragenesis of Copper 
taining the most chlorite, and occurring both diffused and con- 
centrated in seams, appears to have been formed either contem- 
poraneously with the chlorite, or as the next step in the 
rocess, 
The next step appears to have been the individualization, in 
amygdaloidal cavities, of non-alkaline silicates, viz: laumontite 
prehnite, epidote respectively, according as the conditions favored 
the formation of one or the other of these. ; 
Following these came the individualization of quartz in these 
cavities. s 
Perhaps we may be warranted in considering these minerals, 
together with the lime of the calcite that more rarely occurs 12 
this portion of the series, as chiefly due to the decomposition of 
the pyroxenic ingredient of the rock. 
So far as we may infer from the tabulated results, the con- 
centration of c in the amygdaloidal cavities does not ap- 
pear to have begun till after the formation of the quartz. _, 
In this part of the series falls also the formation of a chloritic 
or green-earth mineral, which in some manner has displaced 
prehnite, quartz, calcite, and with which copper, when preset! 
appears to stand in intimate relation. Subsequently to this 
came the individualization of the alkaline silicates, viz: anal 
cite, apophyllite, orthoclase. Here also seems to belong the 
formation of datolite. BC 
The alkaline silicates represent the period of decom pares 
ary minerals, is proof that carbonic acid was very gene nA 
present throughout the whole period of metamorphism ; It cit 
probably the chief mediating agent in the processes, without 
ing sufficiently abundant to prevent the formation of alice 
: change of pyroxene to chlorite, as illustrated 02 the 
oe scale na on e formation of the melephyte a __by 
sp ent of fe and quartz—quartz-porphyty 
chlorite as exhibited tie pabbice ot the pi pase pont & 
an ssoanaay Mi oma line of Oe ag for the rane 
geologist. alteration of the pebbles appears to have 
