426 W. G. Foye — Nephelite Syenites of Ontario. 



comparing the thin-section with the hand specimen, gave the 

 following result : — ■ 



Albite.. 45 percent 



Nephelite... 10 



Biotite 30 



Orthoclase 10 



Pyrrbotite - 2 



Calcite 3 



100 



The twin lamellae of the albite are much contorted. The 

 compressive stresses were able to fracture the minerals of the 

 rock but recrystallization is not found. 



Nephelite occurs as amoeboid grains between the albite crys- 

 tals. It is, also, included in the albite. 



The orthoclase is in allotriomorphic crystals and is usually 

 associated with biotite. 



]STo chemical analysis of this rock type is available. 



5. Pegmatite- Nephelite Syenite. 



Macroscopic description. — The pegmatitic facies of the 

 crescentic laccolith is coarse-grained but is not as rich in 

 nephelite as the nephelite pegmatite of the Gooderham body. 

 It is light bluish-gray in color and is mottled with patches 

 of black. 



The light-colored minerals are feldspar and nephelite. They 

 occur in allotriomorphic crystals from 2 to 3 cm. long and from 

 1 to 2 cm. wide. Grains of hornblende are grouped in masses 

 from 2 to 8 cm. in diameter. These sometimes show a vague 

 schistose arrangement. 



Titanite occurs in crystals 2 cm. long and a centimeter wide. 

 Apatite is present in long slender needles which are light-green 

 in color. Bits of pyrrhotite are disseminated through the 

 rock and sodalite may occasionally be seen. 



Jlicroscopic description. — The following minerals compose 

 the rock in the given proportions by weight : — 



Microperthite 59*02 per cent 



Albite 12-24 



Nephelite 21-42 



Hornblende 4-40 



Calcite 2-40 



Titanite -52 



100-00 



