PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 235 



Diabase. Shale.] 



Meg. A dark -gray, or brown, medium-grained, homogeneous, rather fresh-looking 

 rock; in that respect contrasting with the traps which form the coast series along 

 here; scantily porphyritic with a gray feldspar. 



Mic. The rock reveals an ophitic relation between the auyite and the feldspar. 

 The augite is clouded sometimes by a fine, fibrous alteration, but it is in general well 

 preserved. The olivines are small, rounded, and frequently blackened by irony 

 impurities, especially about their peripheries. 



One section. 



Aye. Manitou(?) 



Remark. The basaltiform structure, the good preservation and the isolation of 

 this rock from the rotting trap of the series forming the shore are reasons for con- 

 sidering this sheet of later date than they, but the association of all these beds with 

 the crumbling, soft, amygdaloidal conglomerates, as well as (further east) with sand- 

 stones, which are fragile, is an indication that they belong above the Baptism river 



basal conglomerate. N. H. w. 



No. 166. DIABASE. 



" Heavy, dark trap, forming the gate to the amphitheater at Temperance river, from the top of the bluff, 

 twenty-two to twenty-five feet." 



Ref. Annual Report, ix, pages 45, 46. 



Mr//. A fine-grained, brownish, diabasic rock, permeated with thalite. 



Mic. The section shows a fine-grained diabase consisting of laths of feldsjxn; 

 augite, //i-n/df/tc and magnetite. The feldspar is twinned by the albite law and shows 

 equal extinction angles as high as 30. A section, which furnished a negative bisec- 

 trix almost but not quite perpendicular, gave an extinction angle of 60. Both 

 results show that the feldspar is labradorite approaching bytoivnite. The augite is 

 mostly in plates of considerable size enclosing the feldspars. Hematite is abundant, 

 and some of the hematite areas seem to represent original olivines. Saponite (thalite) 

 is quite common, but the rock as a whole does not present as altered an appearance 

 as would be indicated by the appearance of the hand sample. Both the augite and 

 feldspar are comparatively fresh. 



Two sections. 



Age. Manitou. u. s. G. 



No. 167. SHALE. (Red.) 



" Ochery, red, shaly beds of grit in a niche in the disturbed amygdaloid under the beds of No. 166, to 3 

 feet; with fine argillaceous films." 



Ref. Annual Report, ix, pages 45, 46. 



A fine-grained, crumbling, often sandy, rather soft, reddish-brown shale. 

 It shows fine, red, clayey films, and a few round blotches of a lighter shade. One of 

 the samples holds part of an apparently rounded fragment of brown amygdaloid two 

 and a half inches in diameter. The amygdules are of saponite and calcite. There 



