48 ES. Dana—Labradorite Rocks of New Hampshire. 
Art. X.—Contributions from the Laboratory of the Sheffield 
Scientific School. No. XXIIL-—On the Composition of 
Labradorite rocks of Waterville, New Hampshire; by EK. 
DANa. 
THE specimens of labradorite rock, which I have had under 
examination, were obtained by Professor Dana last September, 
some minute grains of a magnetic ore of iron, and also a very 
little of a black mineral, probably hornblende. 
he feldspar has a dark smoky color, without iridescence, 
and is beautifully striated. It fuses B. B. with somewhat less 
readiness than ordinary labradorite, and is scarcely attacked by 
acids. It was picked out as carefully as possible, and analyzed 
with the following result : 
T. TI. Til Mean. 
04 51°02 sap 51°03 
Al,O, (TiO,) 26°34 26°07 sien ss 26°20 
" 79 5°13 is 4°96 
14°09 14°23 oe 14°16 
NaO Bs vie 3°44 3°44 
KO es eee 58 58 
100°37 
minute grains of an iron ore, from ;';th to ;},th of an inch in di- 
200 
matter. The peculiar dark-smoky color of the rock is doubt 
less to be explained by the presence of these particles of iro? 
or : 
e. : 
_ This magnetic iron ore, a sufficient amount for the test hav 
ing been picked out by the magnet, gave a decided reaction for 
