R. Pumpelly—Paragenesis of Copper, ete. 347 
Art. XLVIL—The Paragenesis and Derivation of Copper and its 
associates on Lake Superior ; by RAPHAEL PUMPELLY, 
[Continued from pages 188 and 258.] 
Chalcocite, Bornite, Whitneyite, Domeykite.-—Two fissure-veins | 
e 0 a perficially ; 
but it is a remarkable fact that the amygdaloids traversed by 
these veins contain only native copper. One of the fissure- 
short distance. The gangue of these veins is quartz, calcite 
and a carbonate of lime containing some iron and magnesia— 
ankerite ? 
The only other instance I have observed of the occurrence of 
copper in combination with pea og is in the fissure-vein of 
erever this vein has been opened or uncovered, along the 
greater part of its course, north of the Mendota property, only 
nave copper has been found; but when it enters a bed of con- 
glomerate on the north flank of Mt. Bohemia, the little copper 
it contains is combined with sulphur in a very pure chalcocite. 
Where the vein passed from the conglomerate into the underly- 
mg amygdaloid, a fine deposit of chalcocite with calcite was 
found whave been formed, for a short distance, on both sides 
of the vein, between the two beds. 
_ Still farther south the vein enters a mass of syenite, consist- 
ing of a pink triclinic feldspar, some hornblende and much 
chlorite, as an alteration-product of hornblende, and containing 
bornite, Excepting the syenite, wherever copper 1s found in 
traps and amygdaloids on the Mendota property, it is in the 
Phe sacurhinss of the sulphides and arsenides of 
Copper in this isolated manner and in fissure-veins traversing 
* Prof. , after a casual examination of this mineral, suggests that it is 
domorph of chalcocite after ite. ; 
— Serres, Vox. II, No. 11.—Nov., 1871. 
