12 J.D. Whitney on Minerals of the Lake Superior region. 
rence. The diameter of the perfectly formed crystals rarely ex- 
ceeded one-fourth of an inch, although single crystals from this 
locality, octahedrons, have been seen as large as an inch across 
their bases. The finest single crystals, as far as ascertained, are 
from the Cliff mine, and are tetrahexahedrons. One in my col- 
lection, considered by many the most beautiful crystal ever found 
in the Lake Superior region, is about three-fourths of an inch in 
diameter, and nearly perfect. 
the Toltec mine, was found on examination to be chemically 
pure, with this exception, that it contained ;,3,,; of silver, 
about seven ounces to the 2000 lbs, 
olite—F ine crystals of this mineral have been found only 
at the locality on Isle Royale, which has long since ceased to 
worked, the island being now entirely deserted by all except a 
few fishermen. There are several localities on Keweenaw Point, 
however, where it occurs in great abundance, but not, so far as 
I have observed, in handsome crystallizations. The gangue of 
the Hill vein, on the Copper Falls location, consisted, in a portion 
of its more northern extension, of a greenish magnesian silicate 
metrated, in every direction and sometimes forming a sort 0 
reccia, with branches and strings of datholite. It is usually 
massive, translucent, highly vitreous in lustre, and of a light 
 * Pogg. Ann, civ, 339. 
+ mann and Marchand’s Journal, xxvii, 194. 
a 
= PML 
