LE. §. Dana—Labradorite Rocks of New Hampshire. 49 
titanic acid. It is, therefore, probably a very magnetic titanic 
iron, though it was impossible to obtain a sufficient amount of 
the substance for a quantitative determination of the titanium. 
The absence of any octahedral faces or isometric structure in 
the grains is in favor of their being titanic iron. 
n consequence of this impurity, which could hardly be re- 
moved, it is not to be expected that the analysis shoul give a 
satisfactory formula; the result obtained, however, is sufficient 
to prove that the feldspar is unquestionably labradorite. 
e analyses of the mineral, supposed to be chrysolite, 
occurring in yellow, glassy grains, afforded : 
if Mean 
SiO, 38°82 38°88 38°85 
Al,O, tr. r tr 
FeO 28°00 28°15 28-07 
MnO Lag 1°36 1°24 
MgO 30°88 30°36 30°62 
“26 1°60 1°43 
100°08 100°35 100°21 
The oxygen ratio of the bases and silica afforded is nearly 1:1, 
and of the iron and magnesia about 1 : 2; w ence the formula 
(;Fe+3Mg),§. This is then a chrysolite containing an un 
usually large per-centage of iron (here a constituent of the 
mineral, and not owing to the presence of impurities). The 
amount of iron is not strange considering the fact that the 
rock contains diffused throughout it so much free iron ore. _ 
his chrysolite has the same ratio deduced for hyalosiderite, 
bnt still differs widely in fusibility and other characters. It is 
his rock, consisting of labradorite with grains of ore 
feldspar, here in Aa cleavable masses, often half an inch 
long, and a dark mineral, the angle of whose cleavage planes 
proves it to be hornblende, form the mass; together with these 
Am. Jour. Sct.—Tuatrp Series, VoL. III, No. 18.—Jan., 1872. 
i 
