F. H. Lahee — Metamorphism and Geological Structure. 359 

 Fig. 4. Fig. 5. Fig. 6. 



Fig. 



Fig. 8. 



Fig. 9. 



Fig. 10. 



Fig. 11. 



C^£> 



Fig. 12. 



Figs. 4-12. Changes in quartz, which accompany increasing meta- 

 morphism. In fig. 4 the grains are still uncrushed and unstrained, and dis- 

 play their clastic outlines. Figs. 5 and 6 show mottled extinction passing 

 into granulation. In fig. 7 conspicuous granulation is terminal and small 

 muscovite laths have grown a little way into the ends of the quartz grain. 

 Fig. 8 represents zonal granulation, due to shearing. Fig. 9 shows both 

 terminal and zonal granulation and undulose extinction. The curving lines 

 indicate the direction of schistosity. With complete granulation, flattening, 

 and some recrystallization, the original grains become flattened aggregates, 

 as drawn in cross-section in fig. 10. Figs. 11 and 12 are of grains of quartz 

 which owe their elongate shape entirely to recrystallization. 



Fig. 13. 



Fig. 14. 



,7 . 



#^ W' 



vW< #•« 



'" - -£v . 1 " 



Fig. 13. ' Knot ' showing elongation parallel to schistosity and distribu- 

 tion of sericite, thickly plastered against the sides of the ' knot,' but less 

 abundant at its ends. 



Fig. 14. ' Knot ' (partly drawn), showing coarser center and ring-like 

 arrangement of calcite patches containing limonite (black patches). 



