172 R. J. COLONY 



palisades along the Hudson River in New Jersey and New York, 

 the usually resistant aluminous augite has been affected by precisely 

 similar processes, so that in places it is partly converted into a 

 complex of green hornblende (almost actinolite), brown biotite 

 and magnetite dust, frequently associated with end-stage quartz. 

 A quartz-rich phase is found near the top of the same intruded 

 sheet, quartz usually occurring in coarse micrographic intergrowths 



Fig. 3 Fig. 4 



Fig. 3. — Photomicrograph of diorite from Newfoundland. The same rock shown 

 in Figure 2, but taken from another part of the thin section. Nicols crossed, magnifica- 

 tion 20 diameters. The acicular aggregate is actinolite. Note the way in which the 

 late-stage product (white) injects the plagioclase (gray). 



Fig. 4. — Photomicrograph of Palisades diabase. Nicols crossed, magnification 

 20 diameters. An augite crystal (A) with pinacoidal parting indistinctly shown, has 

 been partly converted to a complex of actinolite, magnetite, chlorite and biotite. 

 Quartz (Q) of late-stage crystallization is in contact with the augite. Illustrative of 

 equilibrium changes due to reaction effects between the quartz-alkali rich final consoli- 

 dation product and earlier formed crystals. 



with orthoclase. This is illustrated in Figure 4; an augite crystal 

 (A), showing indistinctly pinacoidal parting, has been in part 

 converted to a complex of actinolitic hornblende, biotite, magnetite, 

 and chlorite; end-stage quartz (Q) is associated with these products, 

 and it seems reasonable to conclude that the quartz-rich alkali-rich 

 liquid residuum must have been responsible for the chemical 

 changes involved, together with equilibrium changes occurring 

 because of the different conditions of temperature and concentration. 



