EXPLANATION OF THE PLATES 



(Photos by H. Gooch, University of Sydney) 



PLATE I 



Figure 1. — Trachyte, Mount Cis, No. J. 1 ( x 35, nicols uncrossed), showing trachytic 

 fabric near vesicle in left top quadrant, also a hexagonal pseudomorph after 

 nepheline to the right of the vesicle, and the pilotaxitic fabric of the rest of the 

 slide. 



Figure 2. — Trachyte, Mount Cis, No. J. 1 ( x 45, nicols crossed), showing fabric. 



Figure 3. — Kaersuetile (?), JEcjirine-Augite Trachyte, Observation Hill, No. J. 3 ( x 35, 

 nicols uncrossed). In the left top quadrant is seen a dark mass consisting of a 

 cluster of grains and rods of reddish- brown camptonitic hornblende. 



Figure 4. — No. J. 3 (again) ( x 45, nicols crossed). Near centre of slide is seen a 

 small idiomorphic brown hornblende crystal. Other grains and rods of the same 

 mineral are scattered throughout the slide. 



Figure 5. — Anorthoclase Trachyte, Entitle. Farm- Glacier, No. J. 54. ( x 35, nicols 

 crossed.) This photo shows a group of anorthoclase phenocrysts (cumulophyre), 

 some of which are at extinction. The base shows along to top and left side of 

 the slide. 



Figure 6— Oligoclase Trachyte, Parasitic Cone of Erebus, No. J. 7 ( x 35, nicols crossed). 

 Slide showing bistre- coloured augite, olivine, mechanically zoned oligoclase and 

 anorthoclase, phenocrysts. 



PLATE II 



Figure 1. — Acid Kenyte (holocrystalline), The Skiiary, No. J. 40 ( x 35, nicols crossed), 



showing microline-microperthite phenocryst near extinction. 

 Figure 2. — Same as Figure 1. Showing strahlenkornig texture of base. 

 Figure 3. — Vitrophyric Kenyte, The Skuary, No. J. 25 ( x 35, nicols crossed), showing 



part of very large rhomb-shaped anorthoclase phenocryst and a smaller micro- 



perthitic felspar near extinction. 

 Figure 4. — Vitrophyric Kenyte, Cape Same, No. J. 48 ( x 35, nicols uncrossed), showing 



an aegirite phenocryst and crystallites in vitreous base. 

 Figure 5. — Phonolitic Trachyte, Erratic, Cape Royds, No. J. 52 ( x 35, nicols uncrossed), 



showing vesicular structure and texture. 

 Figure 6.— Baked Alkali Trachyte, Tuff Cone, Ross Island, No. J. 50 ( x 35, nicols 



uncrossed), showing a large segirine phenocryst. 



PLATE III 



Figure 1. — Leucite Kenyte, Mount Erebus (type specimen) ( x 46, nicols uncrossed), 

 showing anorthoclase phenocrysts and structure of leucitic base. Note the rounded 

 leucite crystals. 



Figure 2. — Oligoclase Kenyte, Turk's Head, No. J. 11 (x 35, nicols crossed), showing 

 twinned oligoclase phenocrysts. 



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