MINERALOGY AND PETROLOGY. 955 



Augite. Diopside.] 



tedly the most likely to have been affected by such action, since they were in a con- 

 dition of flow as long as possible (Nos. 1C, ID, 23, 38, 206), and are wholly ophitic. 

 (b) The granular prevails in the deep-seated, such as the granular gabbros, which must 

 have been least subject to flow (Nos. 1784, 857G). (c) The granular is found in the 

 muscovadytes which have never been in a condition of flow, but stand in their original, 

 often bedded, relations to each other, preserving their original Archean dip (Nos. 667, 

 698, 767, S57G, 857aG). (d) When both structures exist in the same rock, the earlier 

 augitesare sometimes embraced poikilitically in the later (Nos. 515, 2064). It would 

 hence appear that the granular condition is not dependent on the commencement of 

 cooling, (e) The earlier augite is apt to be diallagic (Nos. 291, 292). This indicates 

 that diallage is not a product of late generation, but a feature of the deeper portions 

 of the rock, (f) The granular augitesare about equigranular. If the ophitic augites 

 resulted from crystallization after a state of rest was acquired, the question arises, 

 Why did the earlier augites wholly cease growth, and, while maintaining their 

 existence, refuse to serve as nuclei for the fresh later augites? i. e., why did they not 

 all simultaneously resume the augitic growth, and why did certain new larger 

 crystals of the same mineral start an independent development? 



(4) Augite is frequently seen in a globular, or infantile, condition (Nos. 1092, 

 1334, 1347). This is usually the case in much of the rock muscovadyte (or noryte) 

 and in the gneissic muscovadyte which has resulted from the recrystallization of 

 basic clastic rocks of the Keewatin. Where the original clastic material was more 

 acid, diopside is more common. 



(5) The augite of the granite of Kekequabic lake, and in part at least of that of 

 Snowbank lake, is so supplied with soda that it may be styled aegyrine-augite. It is 

 fully described in connection with Nos. 1094, 1105, 1106, 1399. 



Diopside. In several instances the pyroxene examined has exhibited characters 

 of diopside, i. e., has a cleavage parallel to 010, but in all such cases it is in circum- 

 stances that have indicated the secondary origin of the pyroxene. In No. 132A it is 

 fresh and green, being in one of the augite granites. In these granites it descends 

 (as in No. 643) to globular dimensions and is scattered in that form through the 

 altered feldspars. Without having made careful examination in the "augite gran- 

 ites" of the Keweenewan, it is here only suggested that it is probable that this form 

 of pyroxene prevails in these rocks. (Compare No. 1805). 



It has also been identified in some of the spherulitic and micro-pegmatitic second- 

 ary growths at the contact zones of the Keweenawan (Nos. 132A, 667 ?), where it forms 

 long, somewhat acicular crystals which pierce the altered feldspathic elements with 

 great freedom and in a conspicuous manner. In the diabases where modified by such 

 contacts the same petrographic character has been noted in the pyroxene (No. 137). 



