116 
Rex T. Prider. 
the hypersthene (figure 13B). The hyperstheiie show>s a fine lamellar structure, 
(’leavage is poorly developed, but there is a good j^arting on 010. Although 
l>rownish (due to slight weathering), the weak j)leochroism is still visible. 
Its characters— X a ; Y = b ; Z = c ; (-)2V 83° ; y 1 -765 ; (* 
•--- 1 -74-5 — indicate an iron rich hypersthene with apjjroximately 85 |.er cent 
of the orthoferrosilite molecule (Henry, 1935, p. 223). (‘omparing the above 
data with those given by Henry (p. 223) for tlie iron rich hypersthenes, it 
will be seen that this hypersthene agrees almost exactly with the data given 
for the hypersthene in the eulysite from Mansjo, Sweden, which lias (-) 2\’ =- 
83° ; y == 1-769 ; a 1-751. This is the most iron rich tyjie described 
])y Henry (containing 44-93 per cent FeO). 
Pig. 13. 
Banded eulysitie rocks. 
A. (^uart/v-lienuitite-grunorite rock (No. 17452). 
B. (,)uart/i iimguetlte-liypersthene rock, showing original bed- 
ding preserved in the parallel trains of small magnetite grains 
included in hypersthene. The hy])ersthene is altering along its 
edges and along irregular cracks to a fine fibrous ferro-nntho- 
])hyllite. 
The hypersthene is altering to a more fibrous, highly birefringent am] hi- 
liole, both around its edges and along irregular clacks. Some of the hyper- 
sthenes are eompletely replac'ed by tliis material. The optics of this ami'hibole 
are Z ^ c ; (-) 2V large ; y 1 -687, and it is therefore a ferro-anthojibyllite 
with apjiroxirnately 60 per cent FeSi 03 . 
Quartz and magnetite are the only other constituents with the exception 
of rare apatite. Both are closely associated and there is no sign of reaction 
betw'een them. The magnetite is in liands up to 2 mm. wide and in trains 
of small grains (parallel to the bedding) included in hypersthene. In ]daces. 
tongues of magnetite connect successive bands ol iron ore. The almost 
non-magnetic character of the rock indicates that the magnetite lurs gone 
to fine granular martite, and this is confirmed by the cherry red streak of 
tlie dark bands. On the outer portion of tlie rock the reddisli lu'matite can 
be seen replacing the magnetite, and the change throughout the rock is 
ascribed to oxidation due to weathering. A very different occurreuee of 
hematite is seen in the other specimen from this xenolith which is doserihod 
bc'low. 
