58 Pentti Eskola. (LXHE7 
to cooling at a rather quick rate, as compared with batholitic 
rocks. In such masses the garnets seem to be the richer in 
titanium, the higher the total percentage of titanium in the 
rock. Very probably, however, such titanium-garnets never 
were truly stable. On the contrary, deep-seated batholithic 
eruptives such as those of the Haliburton and Bancroft 
areas in Canada and the sviatonossites have produced garnets 
with low percentages of titanium associated with titanite. 
Likewise at many occurrences at the contacts of limestones 
andradite devoid of titanium proves to have been stable 
in association with titanite. ; 
At the later stages of the mineral development the garnets 
are likely to be freed from a great part of their titanium. 
We may assume these titanium-bearing garnets to be com- 
posed of the same isomorphous compounds as the schor- 
lomite, containing in part trivalent, in part tetravalent 
titanium according to the formula 
Cas(Fe, Ti) (Si, Ti)sO,2. 
The decomposition of this garnet into andradite and 
titanite can possibly take place without any other substances 
partaking in the reaction except the addition of some 
silica, and oxygen. 
A slight, but possibly essential difference between the 
skarn andradites and the garnets from alkaline eruptives 
may be traced in the percentage of magnesium oxide which 
in the former is almost none, in the latter varying between 
a half and some two percent. 
From the above comparison of the different kinds of 
calcium-ferri-garnets we are led to the conception that the 
andradite in the sviatonossites, in spite of its apparent 
magmatic origin, must have been formed under physical 
conditions almost identical with those prevailing at the for- 
mation of the skarn rocks. On the other hand, the crystalli- 
zation of the andradite from the magma has been rendered 
possible by the peculiar chemical composition of the magma, 
no matter how this has originated. 
The pyroxene in the sviatonossite belongs to the 
aegirite-augite series of the monoclinic pyroxenes. 
wi 
+ d - - 
SJ Ne 
Sa TT NRA 
| 
kh ÄRE ARE er AK YE PO 
; 
