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of the larger andesine crystals are frequently more decayed
than the exterior portions, but decay has not progressed greatly.

The second generation of andesine averages 0-75 mm.
diameter, and is mostly tabular to equant,.and sub- to euhedral.
Its composition does not differ appreciably from the larger crys-
tals, and the same varieties of twinning have been observed,
| though pericline twins are less common. Slightly broader albite
lamella may indicate that the second generation of andesine
| is more calcic. The alteration seems less than in the pheno-
crystic andesine.

Orthoclase, whose determination is doubtful, if present at
all is in small amount.

Quartz is up to 1-5 mm. diameter, and quite anhedral,
moulded on the other crystals. It contains strings of minute
doubly refracting crystals, and possesses faint wavy extinction.

The hornblende is the common variety, exhibiting pleo-
chroism in green and yellow shades. It varies greatly in size
and shape, from equant grains 0-1 mm. across to prismatic
crystals 2 mm. by 0-5 mm. It is euhedral, forms the usual
| rhombic cross sections, and is occasionally prismatically twinned.
In some specimens studied the hornblende is quite fresh, in
others it is partly or wholly altered to biotite, chlorite, magnetite,
| calcite, and epidote.

| In texture the quartz diorites vary from fine even subhedral

| grained to those somewhat coarser and of a porphyritic tendency.

| In one thin section studied the order of cessation of crystalliza-
tion was magnetite (some), andesine (phenocrystic), magnetite,
(most) hornblende, andesine (interstitial), quartz.

.
Alteration is not great, on the whole, though as noted above
| certain minerals have been partially attacked.

In the same region are found diorites clearly related to the j
quartz diorites, as they contain andesine of similar habit, similar
hornblende, and titanite. Their colour is whitish grey, and the
hornblende and feldspar are in nearly equal amounts. The
hornblende has a strong prismatic development and is euhedral.
These dioritic rocks are differentiation facies of the quartz
diorite stock.