748 THE GEOLOGY OP MINNESOTA. 



[Diabase. Calrite. 



Mic. Amongst the fine compacted and feebly-interlocking quartz is also inter- 

 locking striated feldspar, the latter being perhaps one-tenth of the whole. There 

 are also a few grains of siderite(?) with rusty surroundings. Shreds of hornblende 

 are scattered throughout the slide, also some sphene and leucoxene. One section. 



Aije. "Huronian." N. n. w. 



No. 16(1."). DIABASE. fCoarsdy porphyntio.) 



As boulders at Algorna. (Compare No. 601.) 

 Ref. Annual Report, xviii, pages 58, 63. 



Meg. Diabasic, with coarse feldspars. 



Mic. The large feldspars are permeated by bands and isolated scales of serf rife 

 and by clusters of zoisite grains. In a section somewhat oblique on extinction on 

 a cleavage is 46, indicating bytou-nite. The pyroxene is frequently twinned on 100, 

 and has a strong cleavage parallel to 100, showing the species to be diallage, and less 

 conspicuous cleavages, seen in basal sections parallel to 110 and TTO. The section 

 also has conspicuous large angular masses of dark leucoxene. With a little liofite 

 and also a little hornblende, the rock is quite a complex and interesting one. One 

 section. 



Age.(.?) 



Ili'inark. This is apparently the rock which exists in form of dike near Silver 

 Islet (No. 601), the coarse feldspar of which has been named Jnn-onife. N. H. w. 



No. 1607. CALCiTE. (Siihfrittitic. ) 



Dietz and Dugan's slate quarries, three miles north of Oarltun. (Compart- No. liili;. j 

 Ref. Annual Report, xx, pages 27, :{:;. 



Mey. Soft, rusty calcareous masses in the slates. These are sometimes a foot 

 or two in longer dimension. 



Mic. The calcite is arranged spherulitically, and in spreading, radial fans, the 

 central part being more highly doubly refracting than the fans. The coarse charac- 

 teristic cleavages form approximate concentric rings round the central part, crossing 

 the fans in curving lines. In some of the interstitial angular areas is a very fine, 

 dusty substance, composed apparently of debris of the same kind as in the slates. 

 One section. 



Age. Animikie. N. H. w. 



No. 1609. CALCITE. (Massive.) 



A mile and a half south of Clocjuet,at the old trial ijuarry in the slates opened by the St. Paul and Puhith 

 railroad. 



Ref. Annual Report, xx, page .'{.'i. 



Mi'!/. An uuweathered portion of the calcareous concretions abounding in the 

 slates. 



