PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 571 



Taconyte. Quurtzyte. Syenyte.] 



Mic. This rock is in general similar to No. 85'2B, and is shown in the accom- 

 panying figure, magnified about thirty diameters. The black represents hematite, 

 and the white, both in and between the granules, represents very fine-grained quartz. 



One section. 



Age. Pebble in Potsdam conglomerate. u. s. G. 



No. 852D. TACONYTE. 



Pebble in No. 852. 



Ref. Annual Report, xiii, page 40. 



Meg. Similar to the last. One of the pieces of this number has two reddish 

 pebble-like forms of finer grain than the rest of the rock. 



Mic. The section is composed of quartz and hematite, in fine grains. There are 

 areas which somewhat resemble the granules of taconyte, although they are not as 

 well denned as in os. 852B and 852C. 



One section. 



Age. Pebble in Potsdam conglomerate. u. s. G. 



No. 852E. QUARTZYTE. 



Pebbles in No. 852. 



Ref. Annual Report, xiii, page 40. 



Meg. Pebbles of vein quartz and of gray to reddish quartzyte, the latter being 

 the larger. 



Mic. The section shows a medium-grained quartzyte, composed of well rounded 

 grains of quartz many of which show enlargements. 



One section. 



Age. Pebbles in Potsdam conglomerate. u. s. G. 



No. 852F. TACONYTE. 



Pebbles in No. 852. 



Ref. Annual Report, xiii, page 40. 



Meg. Reddish, granular taconyte and some flinty taconyte. 

 Mil-. The section shows the usual granular taconyte, the granules being com- 

 posed largely of hematite. 

 One section. 

 Age. Pebbles in Potsdam conglomerate. u. s. G. 



No. 853. SYENYTE. 



Mannheim's silver mine, Duluth, near Rice's point. 

 Ref. Annual Report, xiii, page 40. 



Meg. A rather fine-grained, reddish, granitic rock, composed largely of feldspar. 

 There is some pyrite and some soft, dark mineral present. Vein calcite also occurs. 



