124 WHITE : OATLAND COMPLEX OF IGNEOUS ROCKS. 
The pale green variety, now mostly chloritic, has rather a 
fibrous texture and usually encloses a central patch of a tangle 
of actinolitic blades giving extinction angles of 13 degrees, 16- 
degrees and 20 degrees. In the pyroxenite, however, it is only 
just beginning to take on the actinolitic habit. Pleochroism is- 
very faint in shades of very pale green. The chlorite of which 
the mineral consists, gives, under crossed nicols, a pale indigo 
to bro^vnish-green colour. The alteration product, besides 
chlorite, is epidote and zoisite, the former sometimes occurring 
in parallel strings of disconnected grains. This variety forms- 
about 4.5 per cent, of the total mineral -content. 
The brown or ochreous variety often encloses the former 
and cleavage traces are frequently continuous from one to the 
other. Its pleochroism varies from light-brown — darker brown 
to brownish -ochre — pale straw. It is allotriomorphic and occurs 
not only in isolated patches but is enclosed in streaks and grains 
by the augite. These, and the zones of brown hornblende sur- 
rounding the augite crystals are optically continuous with the 
latter. This bro\\Ti variety is compact and its refractive index 
is higher than the chloritic. Where the former anastomoses into 
the latter its pleochroism changes from brownish-ochre gradually 
to bluish-green and green tints. The mineral is frequently in large 
patches, enclosing idiomorphic aggregates of felspar substance, 
and extinguishes simultaneously over wide areas. Some large 
apatites are also enclosed. This variety forms a proportion 
of the total mass diminishing from 18.2 per cent, to 7.1 per cent. 
Near the quartz vein in the above-mentioned section the pale 
hornblende shows undulose extinction and the chloritic sub- 
stance of which it consists, instead of showing the usual indigo 
in polarised light, gives an olive or brownish -olive colour. Close 
to the quartz the hornblende is clear, with very distinct cleavage 
and the iron -ore in it is streaky as though partially segregated. 
Augite is the mineral most abundantly present in this type. 
Its form is at first somewhat irregular, approaching the quadrate 
in section, then outlines showing well-developed clino-pinacoidal 
faces appear. The dimensions of some crystals almost reach 
3 mm. by 3 mm., but the average size is about 2.2 mm. by 2.0 mm. 
