Hornblende fro}n Italy. — \^on Horn. 371 
an analogous behavior. The prismatic cleavage of the 
hornblende is ver)- good, and the cleavage faces possess a 
splendent luster so that the angle could be determined with 
the goniometer. Measurements on twent)'-five different 
pieces gave an average value of 124*^ 18'. Twins after the 
orthopinacoid (100) occur at times. The mineral has 
a gra}'ish brown streak and a specific gravity of 3.217 to 3.222 
at a temperature of 17° C. At red heat it does not melt, but 
before the blowpipe at white heat it melts to a brown glass 
which is soluble; in hydrochloric acid. 
The pleochroism is very strong: 
a=-li^2:ht yellow (Racide, International Color Scale, oranga 4, u), 
b =brovvn with tinge of red (Radde, vermillion 3, about i-k), 
C= brown with tinge of yellow (Radde, orange 4, about i-k). 
The absorption is b> c> a- The extinction angle was de- 
termined on the prismatic cleavage faces. Twenty-five 
measurements gave an average of 1 1 '^ 5 '. In sections parallel 
to (010) the extinction angle was found to be 14^ 30' to 15^ 
30' c : c- This hornblende was carefully isolated from the 
rock by means of the Klein solution (cadmium borotung- 
state), and this was attended with great difficult)- owing to 
the nearness of the specific gravity of the hornblende to that 
of the diallage also occurring in the rock. The pure min- 
eral was analyzed by Dr. M. Dittrich of Heidelberg, Ger- 
many. He determined the water not only indirectly by 
means of ignition but also according to the direct method 
proposed by Sipocz and Ludwig.* The determination of fer- 
rous iron was carried out according to the method suggested 
by Dolter.f The result of the analysis is found under I, 
while for comparison, three other analyses are given. Un- 
der H is found a hornblende from Vesuvius analyzed by 
Rammelsberg, under HI is a second hornblende from V^esu- 
vius which Berwerth anal}'zed, and finally, under IV is found 
the analysis of a hornblende from the island of Jan Mayen b\' 
Scharizer. 
*E. Ludwig and L. Sipocz, Tschermak's Mitth., 1895, -^ 'ind 
Zeitschrift fiir Anal. Chem., 17, 206. 
tC. Dolter, Zur Kenntniss der Chem. Zus. des Augits, Tschermak's 
Mitth., 1877, 281, and 1880, 100. 
