PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 



641 



Oranite. Tuff.] 



No. 1046. GRANITE. 



From a small island in Kekequabic lake, near the centre of sec. 3, T. 64-7. 

 Ref. Annual Report, xv, pages 361, 364, 395. 



Meg. Purplish red, sub-crystalline in aspect. 



Mir. Similar to the last, but with a little more of the hornblendic mineral. In 

 general, this is coarser than the rock described above (No. 1044), but the same fine 

 matrix lies between all the grains. The original larger grains do not interlock as 

 if crystallized from a magma, but seem to be simply compacted with much secondary 

 deposition. One of the grains of feldspar is nearly surrounded by a clear rim, the 

 central portion being clouded with hematite and alteration, but in general this 

 relation is not noticeable. One (thick) section. 



Age. Archean. N. H. w. 



No. 1047. TUFF. (Modified.) 



Southwest corner of Kekequabic lake; S. W. y sec. 3, T. 64-7. 

 Kef, Annual Report, xv, pages 364, 395. 



Meg. Fine grained, gray, much like No. 1035. 



Mic. There is a fine, gi'anular background, which serves as a matrix for the 

 larger hornblende crystals. This fine matrix consists apparently wholly of a single 

 glass-clear, limpid mineral whose refractive index is higher than that of Canada 

 balsam (dipyre?), but the section examined is too thick to allow of further determi- 

 nation. In this matrix are myriads of actinolHc spicules, whose cross parting per- 

 pendicular to their elongation gives them the appearance of apatite, an impression 

 which is corrected at once on noting their colors of double refraction. 



FIG. 37. SECONDARY (iKOWTH OF HORNBLENDE ON AUGITE FORMS. 



Rock No. 1047. 



