M. FE. Wadsworth —Rocks of Newfoundland. 108 
nally cut by a dike (No. 903) parallel with which run three 
bands of chalcopyrite which lie near the dike. In depth these 
three bands pass into one, varying from six inches to four feet 
in thickness, and the mixed chlorite schist‘and ore of the 
being on the surface and gradually narrowing in depth. The 
_ ore from this locality is mixed chalcopyrite and pyrite with 
quartz, schist, ete. 
e Roberts Arm Mine is worked on two veins from two to 
four feet wide in the eruptive diabase. The veins are com- 
“4 
Lawrence Harbor the old basaltic lava had been pros- 
pected for ore and considerable work done, but the vein is 
simply a gash vein containing quartz carrying pyrite. A vein 
m the shaly argillite had been worked to some extent, but 
showed only some impure graphite with quartz. 
At Hoskins Harbor, Thwart Island, Exploits Bay, a grayish 
black, somewhat indurated, nearly vertical argillite (882), is cut 
by a north and south dike of diabase (881), about twenty feet 
in width. This diabase is cut by a few gash veins of pyrite, 
ing and calcite containing a little chalcopyrite and malachite. 
hese veins had been worked to some extent by persons not 
acquainted with their limited occurrence. The mode of occur- 
activity, after the chief portion of this basalt had 
€xtravasated, the action of percolating thermal waters on the — 
ab ar rock and its fissured and broken adjoining sedimentary 
» led to the concentration and deposition of the copper, 
Iron, and quartz in the places in which they are found.* The 
*See Bull. Mus. Comp. Zool., 1880, vii, 123-131; Proc. Bost. Soc. Nat. Hist., 
1880, xxi, 91-103. 
