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E. S. MOORE 



diopside is primary, some crystals of the diopside which are par- 

 tially altered to secondary amphiboles contain also undoubted 

 evidence of alteration to magnetite and hematite. While these 

 are unusual alteration products for diopside, analyses of this 

 mineral from gabbro sometimes show as much as 15 per cent of 



Fig. 2. — Photomicrograph of diabase showing ophitic texture (crossed nicols; 

 X40). 



iron oxide. The pyroxene is readily recognized as diopside by 

 its characteristic color and extinction angles. 



In texture the ophitic character is usually well developed, as the 

 labradorite generally occurs as lath-shaped, nearly euhedral crys- 

 tals, which penetrate the augite and diopside (Fig. 2) and in some 

 cases are surrounded by them, giving also a poikilitic texture. 

 The rock might therefore be called, to apply the term suggested 



