128 PETROLOGY OF ALKALINE ROCKS 



Figure 3. — Same as Figure 2 (nicols uncrossed), showing leucitic base similar to 



Erebus rock, Figure 1 ( x 46, nicols uncrossed). 

 Figure 4. — Trachydolerite Breccia, Parasitic Cone, Erebus, No. J. 12 ( x 35, nicols 



uncrossed), showing anorthoclase and plagioclase phenocrysts and the asclien- 



structur. 

 Figure 5. — Phyro-pseudohomblende Trachyte, Cape Bird, No. J. 18 ( x 35, nicols 



uncrossed), showing huge magnetite phenocrysts replacing hornblende in trachyte 



base. 

 Figure 6. — Kulaite, Cape Bird, No. J. 36 ( x 35, nicols uncrossed), showing pseudo- 



morph (largely magnetite and felsjtar) replacing hornblende. 



PLATE IV 



Figure 1. — Limburgitic Basalt, Mount Erebus, No. J. 61 ( x 45|, nicols crossed), show- 

 ing olivine and pyroxene phenocrysts with kelyphitic borders, and a vesicle. 



Figure 2. — Same slide showing divergent radial arrangement of the secondary laths 

 after felspar and nepheline. 



Figure 3. — Leucite-N osean Tephrite, Crater Hill, No. J. 31 ( x 35, nicols slightly 

 crossed), showing rims of secondary felspathoid round vesicles. 



Figure 4. — Same slide, nicols not crossed. 



Figure 5. — Magnetite Basalt, Tent Island, No. J. 34 ( x 35, nicols uncrossed), slide 

 cracked ; note small felspar phenocrysts in magnetite base. 



Figure 6. — Leucitophyr, loc. uncertain, No. J. 57 ( x 35, nicols uncrossed). The 

 interiors of the large pseudoleucites have been ground away in making the slide. 



PLATE V 



Figure 1. — Kulaite, Cape Bird, No. P. 325-(648) (x 35, nicols uncrossed), showing 



magnetite pseudomorphs of magnetite after hornblende and also a hypersthene 



pseudomorph with magnetite rim. 

 Figure 2. — Olivine Basalt, Cape Barne, No. J. 49 ( x 35, nicols uncrossed), showing 



magnetite pseudomorph after hornblende. 

 Figure 3. — Andesitic Basalt, Cape Barne, No. J. 2 ( x 35, nicols crossed), showing 



hyalopilitic vesicular ocellar texture. 



