PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 395 



Agates. Aporhyolyte.] 



Meg. The rock is sparsely porphyritic with a striated feldspar. It is in general 

 medium grained and brown. 



.1//V. The section shows an ophitic structure and a spottedness caused by the 

 (iiiyites. The larger augites are less decayed and are less clouded by magnetite than 

 the surrounding rock. The porphyritic feldspar has an extinction angle on the 

 brachypinacoid of 28, indicating labrador-bytownite. In a thinner section made by 

 Marchand, of Paris, may be seen a brilliant orange red mineral in fine grains whose 

 date seems to be earlier than the microlitic feldspars, whose extinction is parallel 

 to a cleavage. It is taken to be bowlingite, an alteration from olivine. There is also 

 a notable amount of a minutely crystalline mineral, so confusedly compact that it 

 gives only an aggregate, yet granulated, polarization or simple darkening. This is 

 probably what was called saponite by Owen, but which probably merits a specific 

 designation of its own. (See No. 91B.) 



Two sections. 



Age. Cabotian. N. H. w. 



No. 519. AGATES. 



"Agates, taken from-the rock at Gooseberry river." 



Ref. Annual Report, x, page 37; Annual Report, xviii, pages 27, 61. 



Meg. Agates, somewhat banded and usually white in color. In the interior of 

 these the quartz is sometimes distinctly crystalline. A little calcite is also present. 

 No section. 



Age. Cabotian. u. s. G. 



No. 520. APORHYOLYTE. 



At one mile west of Splitrock river. Rises from the water in a small bay, and continues eastwardly. This 

 bluff is the source of the red pebbles which constitute the most of the beach at Gooseberry river. The 

 rock does not crumble, but goes to pieces in a multitude of small fragments, which strew the beach and work 

 westward under the action of storms. It belongs stratigraphically above the agatiferous trap at Gooseberry 

 river, and is probably the same as the red granite at the west point of Beaver bay. Compare No. 110. 



Ref. Annual Report, ix, pages 29, 30; Annual Report, x, pages 38, 39, 40. 



Meg. The rock is finely porphyritic with a red feldspar and with quartz, but in 

 the main it appears to be almost amorphous. 



Mic. The great endurance of the pebbles derived from this rock is explained 

 at once by an examination of the thin section, f or it is permeated by poikiliticywarfe. 



In the section is seen an instance of a rather unusual unison of orientation of 

 several small, clear feldspars. The individual crystals are sometimes idiomorphically 

 formed, and show crystal faces and edges. They lie adjacent in the matrix of 

 amorphous red substance, though are not in contact, but they all extinguish at the 

 same instant. The drawing below was made by the use of the camera lucida in order 

 to show this curious combination. In another place in the same section a much 

 larger number of similar grains are grouped. These are, however, not perfect in 



