434 J. L. Smith—Association of Garnet, Idocrase, ete. 
The silica and alumina were impurities, the alumina arising 
from spinel that it had been impossible to separate, and which 
was combined with a little of the magnesia; and these have 
been deducted in making out the oxygen ratio. Moreover, the 
titanic acid obtained in the analysis retained a minute quantity 
of oxide of iron. fter a most careful study of the compo- 
sition as made out by the above analysis, confirmed by sev- 
eral other partial analyses, I feel warranted in giving the follow- 
ing as the true composition of warwickite : 
3B = 105 30°57 
a. = 8 23°58 
6Mg = 121-44 35°36 
1Fe = 36 “49 
343-44 100-00 
The exact formula by which to express this mineral is not 
easily given, as we know nothing of compounds containing bora- 
cic and titanic acid associated together; the expression I am 
disposed to adopt is MgB? + (ig,Fe)T i. : 
I would remark that at the same locality from which the 
warwickite comes, there occurs a titaniferous spinel contain- 
ing about 15 per cent of magnesia, as analyzed by Rammelsberg, 
and would have for its formula 
MgTi + Fei. 
mg7g } im are: ; 
h'm=135° 40’; h'g? (over m) =109°, h'g'=90° 20’-90°30', 
mg =184°20'-184° 35’, g?g' (adjacent)=161° 20’-161° 25, gh? 
(over m)=108° 40’. From these, M. Des Cloiseaux calculates 
mm=91° 20’ and 88° 40’, h'h?=161° 58’, h'm=185° 40’, hig* 
=108° 80, hlg'==90°, mg'=134° 80’, g’g!=161° 10’, gh?= 108° 2’. 
Art. XXXIX.—Curious association of Garnet, Idocrase and 
Datolite; by J. Lawrence Smiru, Louisville, Ky. 
aes at 
