248 TATE: LAKE COUNTRY ROCKS. 
act as a matrix for the quartz, strings of felspars lying between the 
quartz grains. ica, dark brown in hexagonal basal plates: light 
brown tints where the cleavage traces are nearly at right angles to 
the short axis of the polariser. In -sections making a smaller angle 
with the polariser the tint will be darker. Green mica (pleochroic) 
alternating with the above occasionally. Apatite: hexagonal prisms 
abundant, the clear, bright crystals in’ the biotite are cross-sections 
which rotated between crossed Nicols remain dark ; also in stumpy 
and a few fine prisms with parallel extinction. Zircon, a few small 
prisms with obtuse pyramids. Sphene, cuneate brown-olive (pleo- 
chroic), also in erewnne patches. Granules of magnetite accompany 
the green mica. 
(7] White prophyritic granite: Skrppaw. Felspars white, turbid 
(exam mine by reflected light). Orthoclase : note ‘schiller’ fibrillation. 
Oligoclase giving Carlsbad and albite twining. J/zca red- brown. to 
e honey yellow, with some green and even colourless from loss of 
iron, now gathered up, forming secondary magnetite grains. Quartz 
{with numerous moving bubbles), in clear tints, rainbow margins, 
allotriomorphic, filling the interstices between the above constituents. 
Apatite as small square or rod-like prisms: highly refractive but 
colourless; first evolved and therefore present in all the other 
components. Zidofe after felspar and biotite where these are in — 
contact: colourless, with brilliant _ tints. Chilorite (green) after 
biotite here and there. 
[29] Biotite grme: Eskpate. Quartz in irr grains 
enclosed by the felspar which sometimes penetrates shen multitude 
of minute cavities arranged in linear symmetry : note ‘strain-shadows,’ 
between crossed Nicols. ée/spars kaolinised (giving ‘aggregate 
polarisation’), and a chloritoid substance, feebly pleochroic along 
cracks. Orthoclase, Carlsbad, and ofegoclase with albite twinning. 
Biotite dark brown to honey-yellow and green to colourless 
(pleochroic) : basal sections hexagonal, isotropic: prisms across 
e. vage traces much bent. Afafize in six-sided cross-sections, clear, 
colourless and highly refractive i Epidote is a secondary 
constituent where biotite and fels spar lie in contact : it is scolourless 
by ordinary light. but — in brilliant tints. Agee nF 
| grains. 
- [33] Aplite: a “fine-grained vein: intrdsive. in. Rekidale granite a 
at WABERTHWAITE, Micropegmatitic : the felspars are chiefly 
ie thoclase with clase in part, and microcline. Quarts in cleat 
= — on for the very minute pores) Peotties the Snes a 
' ied ——— oe 
