172 THK GEOLOGY OF MINNESOTA. 



[Diabase. 



No. 94. DIABASE. (Fine-grained.) 



Top of bluff, west side of Agate bay. 



Kef. Annual Report, ix, page 26. Annual Report, x, page 37. 



Meg. A very fine-grained rock, dark gray and brownish in color. Along small 

 cracks, and sometimes where there are no cracks visible, the rock is colored a dark red. 



Mic. Minute lath-shaped fe/i/xjiarx occurin connection with magnetite, hematite 

 and augite, the latter sometimes in small plates embracing the feldspars, but usually 

 in minute grains between the feldspars. This augite in grains is crystallized with a 

 feldspathic base of very minute grains, and the augite and feldspar fill in the spaces 

 between the lath-shaped feldspars. 



One section. 



Age. Cabotian. u. s. o. 



No. 95. DIABASE. ( Amygdaloidal. ) 



West side of Agate bay; underlies No. 94. 



Ref. Annual Report, ix, page 26. Annual Report, x, page 37. 



Meg. A very fine-grained, brown rock, with abundant amygdules of pinkish 

 laumontite. Some of the amygdaloidal cavities are lined with a yellow mineral, 

 probably epidote. 



Mic. Small lath-shaped plagioclases in a background of augite, magnetite and 

 abundant hematite. The amygdules are filled with laumontite, and this mineral has 

 often penetrated into the mass of the rock. 



One section. 



Age. Cabotian. u. s. G. 



No. 96. DIABASE (iviili olivine). 



One of the alternating beds at Agate bay. This layer underlies an amygdaloid, No. 95. 

 Kef. Annual Report, ix, page 26. Annual Report, x, page 37. 



Meg. It is heavy, firm and dense; though with a few small amygdaloidal spots. 



Mic. Feldspars appear as microlites, and frequently exhibit ophitic relation 

 with the augite. Magnetite and hematitic coloration are in the usual amount. Olirinc 

 is also distinguishable. The rock is similar to many others already noted. 



Two sections. 



Age. Cabotian. N. H. w. 



No. 97. DIABASE. (AniiKjddMual.) 



West side of Agate bay; underlies No. 96. 



Ref. Annual Report, ix, page 26; Annual Report, x, page 37. 



Meg. Almost exactly similar to No. 95, which see. 



No section. 



Age. Cabotian. u. s. G. 



