WHITE : OATLAND COMPLEX OF IGNEOUS ROCKS. 
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hornblende, but in such a fashion as to suggest that the latter 
was rather later in crystallising. However in some cases an 
individual of fibrous amphibole with an extinction of 15° is 
•enclosed. Apatite in prismatic forms is the other usual mineral 
that is enclosed. 
In the process of decomposition, besides varying amounts of 
•epidote, there has usually been a fairly heavy separation of iron- 
ore, mostly titano-magnetite. 
The additional fact that the biotite in the acid facies has 
commenced to form at about the same relative period as the more 
oxidised variety, which occurs in the intermediate and basic facies 
of the complex, affords confirmation of the micaceous character 
of this mineral if not of its close identity with the less altered 
biotite. 
Hornblende is present in increasing quantity from the centre 
to the margin of the boss, but in the normall}" acid facies it does 
not amount to more than 7 per cent, of the total mineral content 
and from the most acid specimens in the facies it is nearly absent. 
Here it is greenish in pseudomorphs of chlorite and is usually 
associated with the biotite. In one case the alteration product 
has the structure of helminth. The crystals are sub-idio- 
morphic with pleochroism light-green — darker green. Its angle 
of extinction appears to be only about 5 degrees. It occasionally 
encloses many needles of a mineral which also extinguishes at 5 
degrees, and in one individual these lie along three planes, thus — 
Fig. 7. 
