eee Wee ees Pk ee 
J.D, Whitney on Minerals of the Lake Superior region. 17 
Orthoclase has been recognized and described as occurring in 
the mineral viens of Schemnitz and Kongsberg,* although ” 
ossibility of such an association has, until within a few year 
een hardly allowed. The well- established fact of the eins 
of feldspar as a pseudomorph, of the form of laumontite and of 
analeime, in the trap of the Kilpatrick Hills, near Dumbarton, 
Scotland, furnishes incontestible evidence of the pores of 
the formation of this mineral in the moist way, and the phenom- 
ena exhibited on Lake Superior in connection with the associa- 
tion of feldspathic and zeolitic minerals, point as clearly to this 
conclusion as they do to the necessity of rejecting the igneous 
theory of the origin of the veins themselves. 
The variety of orthoclase of which the analysis has been 
given above is found in almost all the mines, from the extremity 
of Keweenaw Point to the Ontonagon; but in the latter district 
it is most abundant. At the Northwestern mine, the association 
of orthoclase and analcime is almost constant, and there are aie} 
geodes which do not exhibit delicate erystallizations of the 
named mineral so situated with reference to the other as to lead 
to the conclusion that their formation must have been going on 
at the same time and under the same circumstances. The vt 
eral, w 
is nie sa ea but of which rhe never been able to 
— enoug an analysis. This mineral seems to have 
the last ea of all the vein-minerals of this: is a sia: 
oan by it. The same may be said in siterenael to oe joint 
~ occurrence of natrolite and orthoclase * this locality. 
clear evidence here of the contemporaneous formation of t the 
oe natrolite, calcite and orthoclase. 
Ontonagon region, the minerals associated with ortho- 
have been noticed ; in the same connection. At the Minnesota 
mine, the large crystals of quartz, formerly obtained there in 
abundanee, were frequently encrusted with a thin layer of crys- 
tals “i orthoclase. 
may be remarked, that the crystals of this mineral are, 
iBiou gto the whole copper region, remarkably uniform in 
* See Leonhard and Bronn’s Jahrbuch, 1850, goad 43; also Bischof’s Geology, ii, 330, 
SECOND SERIES, Vor. XXVIII, No. 62.—JULY 
3 
