95 
The sections appear fresh, though a fine ground mass is here 
and there noticeable, connecting the individual minerals : this 
is the result of crushing. 
The quartz occurs as small grains, with irregular or 
rounded boundaries, with numerous fluid pores arranged in 
parallel bands or scattered. 
Felspar predominates : microcline crowded witli inclusions 
(unindividualised) more or less grouped : a very small amount 
of plagioclase is present. "Strain shadows" are much in evi- 
dence. 
Mica occurs as a dark, brownish-green biotite, with 
prism axes roughly parallel ; some flakes have undergone par- 
tia»l decomposition peripherally, with the production of a 
green, fibrous mineral. 
Magnetite, as opaque particles, with no definite boundary, 
rarely idiomorphic, elongate, frequently enclosed by biotite. 
Zircon is fairly well represented as inclusions in the 
microline appearing with the lather rare elongated prismatic 
habit. The prisms polarise with red and green interference 
colours under crossed nicols ; they are not surrounded by a 
Dleochroic halo. 
Epidote produced at the expense of the felspar, as coloar- 
less or faintly yellowish individuals, without definite form. 
Some of the felspar individuals can be observed to be parti- 
ally converted into epidote, the latter appearing (with crossed 
nicols) as very numerous brilliantly coloured specks, almost 
entirely obliterating the characteristics of the felspar. 
The gneiss in many respects resembles a granulite, 
though gainets, usually characteristic of granulites, are en- 
tirely absent. 
The rock seems beyond doubt a "metapyrigen gneiss." 
Gneiss. 
Plate xvi. , fig. 2. 
Locality. — Mann Ranges, south-west of Mount Samuel. 
MacroscopicaUy.— A compact granitic rock, w^ith a ten- 
dency to foliation, the mica in elongated patches, whose major 
axes point in one direction ; advanced in decomposition super- 
ficially. 
Microscopically. — Texture granular with a quartz-ortho- 
clase mosaic, and larger felspars embedded in a crushed 
groundmass. 
Quartz clear, with gaseous and liquid inclusions, ar- 
ranged more or less distinctly in streaks : also few individual- 
ised inclusions of elongate-rounded form, the largest measur- 
