PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 887 



Jasper. Quart?, and red jasper.] 



If on the other hand this copper existed in the Arehean prior to the Keweenawan 

 other important corollaries are evident. 



1 . The conditions precedent for the development of metallic copper in connection 

 with basic eruption existed in the Arehean before they existed in the Taconic. 



2. Metallic copper in the Arehean may be the direct source of that of the 

 Taconic, through the fusion and complicated chemical reactions attending the 

 transformation of the basal (Keewatin) greenstones into gabbro and diabase of the 

 Keweenawan. Arehean metallic copper or copper ores, and the Keewatin iron ore 

 may have locally gone together into the composition of the gabbro and diabase of 

 the Keweenawan. 



3. If that be the source of the metallic copper of the Keweenawan, it implies 

 the probable present existence of large bodies of copper in the Keewatin, but probably 

 at great depths within the Lower Keewatin. N. H. w. 



No. 2279. JASPER. (Red.) 



From the dump of the Lee mine, near Tower. 



Ref. Annual Report, xxiv, page 84. Compare No. 140. 



Meg. Brick red, dense, but on a freshly fractured surface' presenting an internal 

 structure that shows numerous small and irregular conchoidal vitreous surfaces which 

 resemble irregular cleavages. There are in the mass a few small, scattered, massive 

 hematite grains of considerable size, also smaller ones of quartz, which latter also 

 forms a few thin veins, and still fewer specks of a yellow sulphide, which resembles 

 chalcopyrite. The entire mass seems not only to be finely crystalline, but to belong 

 to the hexagonal system, resembling quartz. On the fresh surfaces mentioned are 

 seen numerous dull faces which were produced by the separation of a crystal from 

 its neighbors. These are sometimes grouped so as to suggest the hexagonal system 

 with terminal pyramidal or other faces. 



Mic. The coloring material is hematite. This is mainly as a pigment, but 

 occasionally takes the form of minute, cherry-red, sub-translucent scales and crystals. 

 The whole section breaks up, between crossed nicols, into angular, " patchy " areas 

 of poikilitic quartz which have varying orientation. The rock might be called a 

 vitreous quartzyte except for its fiery red color. 



Aye. Lower Keewatin(?) 



Remark. It is unfortunate that the structural relations of this rock with the 

 greenstone and the ore are unknown. N. H. w. 



No. 2280. QUARTZ AND RED JASPER. ( Spongy. ) 



Same place as No. 22711 ; a portion of the same rock. 

 Kef. Annual Report, xxiv, page 84. 



M'<j. A harsh, siliceous, spongy mass, the cavities evidently due to the oxida- 

 tion and removal of pyrite. The siliceous remnant consists in part of red jasper, the 



