PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 741 



Granite and diabase. Calcite, laumontite.] 

 Serpentine. 



No. 1541. GRANITE AND DIABASE. ( <\n<twt ^in-in/cu .) 



Duluth. On the Weller road, so-called, one and one-half miles from lake Superior, but about two miles 

 from the business part of Duluth. 



Ref. Annual Report, xviii, pages 26, 61. 



Meg. A specimen showing the contact of Nos. 1540 and 1542. The two rocks 

 are closely welded together; the contact plane is sharp and distinct and there is 

 practically no blending of the two rocks, but the dark rock (No. 1540) has some 

 reddish feldspar in it. Neither of the rocks is particularly finer grained at the 

 contact. No section. 



Age. Cabotian. u. s. G. 



No. 1542. GRANITE. (Bed.) 



Duluth. On the Weller road (formerly so-called), now Piedmont avenue, at about two miles from the 

 business part of the city. 



Ref. Annual Report, xviii, pages 26, 61. 



Meg. Crystalline, red, with some light-green spots. 



Mir. The red, striated feldspars are surrounded by quartz which has also in 

 some cases insinuated itself into the feldspars in a micropegmatitic manner. The 

 latter are zoned by differing shades of hematitic redness. There is (or was) a little 

 green hornblende, but it is largely chloritized. About these hornblendic spots can be 

 seen remnants of pyroxene in isolated areas and grains. One section. 



Age. Cabotian. 



lii'iHtir/,: The rock appears to have been at first a part of the gabbro, but is 

 now much altered by its contact on the elastics. N. H. w. 



No. 1544. CAI,(.MTE, LAUMONTTTK. ( \'<-in nmti-rinl. j 



,FYom a \cin in the gabbro at Rico's point, Duluth. 

 Jief. Annual Report, xviii, page (!1. 



Meg. A roughly banded vein, an inch to an inch and a half in thickness, 



composed of calcite and laumontite, with some serpentine-like material on the 



surfaces. No section. 



Age. Vein in Cabotian rocks. u. s. G. 



No. 1545. SERPENTINE. 



In a vein in the gabbro at Rice's point, Duluth. 

 Ref. Annual Report, xviii, page 61. 



Fine, yellowish. 



Mir. The nearly isotropic substance shows a cloudiness distributed character- 

 istically of serpentine, in which are the remnants of some highly polarizing ferro- 

 magnesian minerals (jt//n>.inie ? ), and occasionally of a twinned feldspar, with 

 disseminated calcite. One section. 



Age. Cabotian. N. H. w. 



