﻿658 MR. J. A. HOWE PETEOLOGICAL NOTES [Aug. I905, 



No original clastic structures are visible, and probably all the 

 quartz has recrystallized. Where the massive ore is absent a red 

 iron-oxide staining surrounds all the quartz-grains. 



No. 12, Mount Yagu. — A foliated quartz-iron-ore schist, 

 similar to 13, described below. 



No. 13, hill south of Mount Combe.— A fine-grained iron-bearing 

 quartz- schist. A few streaks of magnetite run through the 

 slice, and small crystals of the same are scattered evenly throughout 

 the whole rock : in addition, there are numerous minute crystals 

 of haematite which are generally isolated, but in places are 

 aggregated into small masses. 



No. 53, Mount Tiberi (microcline-granite gneiss). — A pale 

 granitic-structured rock, of moderately-coarse grain, showing dull- 

 white felspar, clear felspar, and quartz. Muddy-looking hypidio- 

 morphic felspars, often with a narrow clear margin, are set in large 

 plates of microcline. The clouded felspar appears to be mostly 

 oligoclase, the alteration-product being principally mica. Quartz 

 occurs in patches and blebs within the microcline. Green chlorite- 

 patches probably represent hornblende, and are quite subordinate 

 in amount. Epidote, sphene, and apatite are present. 



Microperthitic structure is seen in some of the microcline. 



No. 36, Mount Combe (microcline-granite gneiss). — A fairly 

 coarse-grained rock, with pale- green felspar, white felspar, quartz, 

 and hornblende. 



The slice shows phenocrysts of orthoclase and oligoclase, 

 with clouded centres (micacized and epidotized) and clear fresh 

 borders. 



Microcline is abundant in large plates, enclosing the quartz 

 and felspar. Epidote is common in grains within the altered 

 felspars, and also associated with hornblende. The latter mineral 

 is in idiomorphic green crystals and plates ; chloritic alteration 

 appears in places. Quartz is present in large irregular plates 

 between the felspars. Apatite in stumpy crystals, magnetite 

 in small grains, and leucoxene in patches also occur. 



No. 35, Mount Combe. — A pale-greenish rock with dark spots. 

 Yery similar to No. 36. Idiomorphic orthoclase, and probably 

 oligoclase and andesine, occur in short prismatic crystals with 

 mica, epidote, and zoisite as alteration-products in their cloudy 

 bodies. Microcline (and perhaps orthoclase) encloses the older 

 felspars, and also includes small round blebs of quartz. Quartz 

 also occurs in somewhat large plates with postsynthetic structure. 

 Green hornblende is present, usually idiomorphic. Epidote is 

 frequently associated with the hornblende. Sphene occurs in 

 large masses, and apatite in small prisms. Magnetite in cubes 

 generally accompanies the hornblende. 



