498 J. Allan Thomson—Inclusions in Maia Rocks. 
Analogies amongst 
Mineral combinations of Kakanui Analogies amongst 
inclusions. eT eee plutonic rocks. 
A. (1) Spinel, green augite, olivine ...| Olivine nodules. Lherzolite. 
(2) Spinel, green augite, olivine, Hornblende lherzo- 
brown hornblende Hornblendic olivine lite. 
(3) Spinel, green augite, olivine, nodules. F 
brown hornblende, garnet Hornblende eulysite. 
(4) Spinel, green augite \ Ariégite. 
(5) Spinel, green augite, garnet Eynoxerie modules; Garnet ariégite. 
B. Black augite, garnet, with or with- New type of Basic aridcit 
out hornblende and magnetite pyroxene nodules. ppaigso: 
C, Hornblende, subsidiary garnet, and Hornblendite and 
biotite Hornblende nodules, hornblende ariégite. 
The types grouped under A differ from ordinary olivine nodules in 
the absence of enstatite and the comparative rarity of olivine. 
Lacroix, however, notes! that besides normal olivine nodules there 
exist more basic types characterised by the presence of brown basaltic 
hornblende, which moulds all the other elements, and that these are 
sometimes poor in enstatite and even in olivine and picotite, while the 
chrome-diopside is replaced by augite. The presence of garnet has 
not, so far as I can find, been noted in olivine nodules. The green 
augite resembles the chrome-diopside of lherzolite in colour and in 
microscopic appearance, but it presents at times an incipient diallage 
structure. The spinel is generally a green pleonaste, more rarely 
a brown picotite. This mineral is stated in textbooks to be without 
cleavage, but in one section a beautiful cubic cleavage may be 
observed. The garnet is of the pale-rose colour seen in the garnet 
ariégite of the Pyrenees. 
The types grouped under B differ from any well-known plutonic 
rock or inclusion of volcanic rock. It is still open to question 
whether they are really homceogenous inclusions, but I incline to this 
view because of the presence of brown basaltic hornblende and the 
general similarity of all these rocks to the basic rocks accompanying 
lherzolite in the Pyrenees. The augite has in hand - specimens 
a bottle-glass appearance with conchoidal fracture and a jet-black 
colour, translucent on thin edges. In thin sections it has a pale bistre 
colour, almost without pleochroism, and a fair cleavage, on which 
extinction angles up to 41° have been observed. It contains as 
inclusions regularly arranged rows of rounded or elliptical grains of 
iron ores, sometimes black and opaque, sometimes translucent and 
reddish, crossing the cleavage at a considerable angle. The garnet is 
of a red-brown colour, and is evidently different from that occurring 
in the types under A. 
The commonest type of the rock consists only of the augite and 
garnet in thoroughly allotriomorphic forms. The augite sometimes 
includes the garnet, and vice versd. With the incoming and pre- 
dominance of brown hornblende, which moulds the augite, the rock 
passes over to the next type. 
1 Loe. cit., p. 486. 
