XVI LIST OF ILLUSTRATIONS 



PBft 



2. Quartz— showing highly modified development of quartz crystals 



occurring in miarolitic cavities "^l 



3 Albite— showing common habit of albite crystals occurring in miarolitic 



cavities ^'* 



4. Diopside ; prismatic crystal from miarolitic cavity 44 



5. Albite; showing prismatic development of colorless transparent albite 



crystals occurring in fractures and veins 55 



6. Epidotc. Crystallographic drawing in clinographic and orthographic 



projection of epidote of the hourglass type 58 



7. Epidote. Sketch showing optical directions and hourglass structure. 



Projection on a (100) 58 



8. Epidote. Projection of "hourglass" crystals on b (010) showing 



optical orientation 59 



9. Axinite. Showing common habit of crystals from Goose Creek. 



Orthographic and clinographic projection on c (010) 61 



10. Prehnite. Type 1 crystal. Orthographic crystal drawings 62 



11. Prehnite. Type 2 crystal elongated on the b axis showing crystal 



habit and striation of c (001) 62 



12. Prehnite. Type 3 elongated on the a axis showing striation and crys- 



tal habit in orthographic and clinographic projection 63 



13. Prehnite. Type 1 showing common "hourglass" form 63 



14. Prehnite. Type 1 showing a modification of the "hourglass" struc- 



ture where the two end sectors are not connected 64 



15. Prehnite. Type 1 showing "hourglass" structure in a crystal bounded 



only by pinacoids 64 



16. Prehnite. A variant of type 1 showing the growth of thickening at 



the ends to produce sheaves 64 



17. Prehnite. A side view of crystal aggregate similar to that shown in 



figure 16 '_ 65 



18. Prehnite showing optical structure of crj'stals of type 2 65 



19. Prehnite showing optical structure of crystals of type 3 65 



20. Datolite of first generation showing acute habit 66 



21. Datolite of second generation showing more prismatic habit by 



elongation on the a axis 67 



22. Datolite of second generation showing pronounced tabular develop- 



ment parallel to x (102) 70 



23. Chabazite showing unit rhombohedron, the common form at Goose 



Creek 71 



24. Stilbite of "Epidesmine" habit bounded only by three pinacoids 72 



25. Stilbite of the usual habit showing pyramidal faces 73 



26. Laumontite showing common habit, the unit prism with the negative 



dome e (101) 74 



27. Apophyllite of cubic form showing only prism and basal pinacoid 75 



28. Apophyllite showing commonest combination of pyramid with small 



prism faces 76 



29. Apophyllite showing combination of pyramid with faces of four prisms _ 81 



30. Apophyllite from specimen of Merrill and Wherry showing two prisms, 



pyramid and base 82 



31. Calcite showing the commonest habit of amber colored calcite occur- 



ring in the veins 83 



32. Calcite. Habit of a single white crystal observed resting on prehnite. 84 



