166 THE GEOLOGY OP MINNESOTA. 



[Diabase. 



ically, of the chief gabbro mass which lies further north. The lavas and clastic rocks 

 along the shore seem to be the more distant representatives of these coarse diabases. 

 How many of the surface outcrops of these coarse rocks away from the lake shore, 

 belong to sills, and how many are of massive surface flows, there is at present no 



way of knowing. N. H. w. 



No. 89. DTABASK. 



Just east of the creek crossing sections 9 and 10, east of the mouth of French river, and near Sucker bay. 

 Kef. Annual Report, ix, page 24; Annual Report, x, page 30. 



Meg. A massive, homogeneous, fine-grained diabase-like rock, non-amygdal- 

 oidal, but having large geodic concretions of calcite, with an interior of laumontite. 

 The joints, as seen in the field, are lined with a mineral Norwood styled heulandite. 

 Compare Nos. 515 and 516. 



Mic. An ophitic diabase of the usual characters, lath-shaped feldspars, />//mrr//r 

 much changed, magnetite, nlirin<\ li<'>n<if!t<'\ rh/<-!t<', a little </inirf~. 



One section. 



Age. Cabotian. N. H. w. 



No. 90. DIABASE (u-ith olivine, course). 



From the east point of Sucker bay; a massive, heavy bedded, dark rock, sloping up from the water's edge, 

 similar to Nos. 1 and 49; continues to Knife river; also forms Knife islands. 



Ref. Annual Report, ix, page 24; Annual Report, x, page 139; Proceedings American Association for the 

 Advancement of Science, vol. xxx, page 162; Bulletin ii, page 99. 



Meg. A rather coarse-grained, granular " sugary '' appearing rock, which is made 

 up of plagioclase, weathering white, and black materials. 



Mic. The following is Dr. Wads worth's description (Bulletin ii, page 99): 



" One section is composed of numerous grains of olivine and masses of augite 

 arranged irregularly in the feldspar which is sometimes in aggregations of crystals, 

 and sometimes in divergent lath-shaped blades dissecting the augite. The feldspar 

 contains the remains of an included globulitic base, so commonly seen in the 

 plagioclase of modern basalts. 



" The olivine is much fissured and more or less altered to a greenish serpentine. 

 Greenish and yellowish brown secondary products, showing aggregate polarization, 

 are common in the section. In another section of the same rock the feldspar 

 contains much of the altered globulitic base, while that mineral is largely in rounded 

 and tabular aggregations of crystals. The olivine is here altered, not only to the 

 greenish serpentine, but also to a brownish yellow form." 



Two sections. 



Age. Cabotian. u. s. G. 



Remark. This, perhaps, is in continuation of the coarse diabases Nos. 85, 87, 

 and they are probably all closely related with the great gabbro mass seen at Duluth. 



N. H. w. 



