126 WHITE : OATLAND COMPLEX OF IGNEOUS ROCKS. 
SUGGESTED AFFINITIES. 
The augite-homblende diorite, besides resembling many 
of the " greenstones " found in the Isle of Man, is, from its 
estimated chemical composition, comparable with some of the 
augite diorites in Minnesota and the hornblende -augite diorite 
from Inchnadamf. It probably approaches the composition of a 
shonkinite chemically. The most basic tyi[>e would closely 
resemble the composition of a pyroxenite from Brandberget, 
Gran. Norway. 
3. INTERMEDIATE TYPE. 
This type has variable characteristics, but on the whole 
combines those features which distinguish both the acid and 
basic types. Specimens arranged in series of decreasing pro- 
portions of quartz do not show a corresponding increase of augite 
and vice versa, and no specimens have yet been found with both 
these minerals absent. This variable character suggests that 
the intermediate facies is a mixture rock." 
QvAirtz, when it occurs, is very rarely fractured, and is 
crowded with fluid cavities. There is also an inclusion of an 
undetermined mineral of prismatic form with blunt pjTamidal 
ends, cross fracture, refractive index apparently less than that 
of quartz, Aveak birefringence and doubtful pleochroism in faint 
blue and yellow. In the basic xenolith previously mentioned 
the quartz seems to have separated previously coterminous and 
interlocking crystals, to have torn off minute ragged pieces of 
the fibrous hornblende and to have partially re-fused the felspar 
substance towards the boundaries of the fragment. 
Felspar. Where quartz is in small quantity or absent, the 
felspathic mineral is practically aUotriomorphic. Elsewhere 
the forms are usually prismatic, some are sub-idiomorphic and 
some have still more irregular outlines. The average size is 
about .6 mm. by .3 mm. It is extremely decomposed so that 
the genus is quite undeterminable, but the alteration products 
are quartz, calcite, an epidote or zoisite and amorphous matter. 
No white mica could be found. Inclusions are very rare. 
