and its associates on Lake Superior. 195 
in diameter of prehnite, greenish-white, or tinged with pink 
generally amorphous, but often with a radiating structure, and 
sometimes slightly impregnated with native copper. 
The portion of the bed nearest the hanging wall is often 
highly amygdaloidal, while the matrix has at the same time a 
different degree of hardness, texture and color, and often a 
different mineralogical constitution from the parent trap. These 
varieties form the 
Amygdaloids proper. 
The amygdaloids are the most highly altered form of the 
melaphyr, and present themselves under a variety of characters 
in different beds and in different parts of the same The 
colors of the matrix are different shades of brown or red, and 
of green, or of these mixed; its texture varies from fine grained 
or sometimes subcrystalline to compact; and its hardness ranges 
from that of limestone to that of quartz. 
Two quite different kinds of amygdaloid occur on Portage 
Lake, both separately, and intimately associated in the same 
, and are easily distinguished by their different colors, the 
one being brown and the other green. ee, 
_The brown, which exhibits the amygdaloidal character in Its 
ighest development, has a chocolate-brown to dirty red matrix, 
which general]: is easily scratched with the knife, but 1s some- 
€s indurated and hard; it has a fine grained to subcrystalline 
texture, and now and then contains minute reddish crystals of 
feldspar, and fuses easily to a dark-green and somewhat mag- 
hetic glass, 
tarely empty, are laumontite, leonhardite, calcite, quartz, a 
steen mineral, apparently green-earth, delessite (more rarely), 
native copper. eplnts prehnite, analcite, orthoclase. In places 
green variety is a very fine grained to compact oy ie 
‘green rock. It is generally very hard, s - fire 
under the steel. Its constituents are V' ely free silica, 
green mineral which has been generally taken for epidote, 
1 ina er it cult 
toa dark enamel which gelatinizes with acids. These 
are called epidote “ wea aed they are probably in ord 
ates, at least, an intimate mixture of ae and epidote, 
ough in otherwise nearly similar beds, the green ninest 
S soft, and is probably either a green-earth or a chiorils: 
t 
