1916] THE GROWTH OF ETCH-FIGURES 267 
Fig. 25, 26. Asymmetrical pits, same mineral, same conditions. 
Fig. 27. Pits occurring above and on either side of edge of twinning 
plane, Diopside, Zillerthal (010), same corrosive, 33/4 minutes. 
Fig. 28. Typical flat-bottomed pit, like Greim’s second type, Diopside, 
Zillerthal (010), same corrosive, 1834 minutes. 
Fig. 29. Typical pit, Diopside, Zillerthal (100), 50% Hydrofluoric Acid, 
61% minutes. 
Fig. 30. Pit on Diopside, Zillerthal (101), dilute Hydrofluoric Acid, 100°, 
20 minutes. 
Fig. 31. Pit on Diopside, Zillerthal (101), dilute Hydrofluoric Acid, 100°, 
30 minutes. : 
Fig. 32. Pit on Diopside, Zillerthal (oor), 50% Hydrofluoric Acid, 100°, 
20 minutes. 
Fig. 33. Pit on Diopside (110), fused Calcium Chloride, 15 seconds. 
Fig. 34. Pit on Diopside, Zillerthal, same corrosive, 30 seconds. 
Fig. 35. Colemanite etched with 10% Hydrochloric Acid, 100°, showing 
“crack beak”’. 
Fig. 36. Colemanite, 2% Hydrochloric Acid, 100°, showing the position 
of pits on adjacent sides of a cleavage plane. The line sur- 
rounding indicates the corners of the fragment. 
Fig. 37. Plaster model of diopside crystal. 
Fig. 38. Model of theoretical pit on the base. 
Fig. 39. Model of theoretical pit on orthodome. 
Fig. 40. Model of theoretical pit on orthopinacoid. 
Fig. 41. Model of theoretical pit on prism. 
Fig. 42. Model of theoretical pit on clinopinacoid. 
