Lopiz. 505 
a 
2, Eaternal Characiers. 
‘Fhe siueiure of this mineral is always distinctly foliated 
at right angles to the axis of the prism, and often the folia are 
quite brilliant ; but more frequently little more so than feldspav. 
it cleaves also insome specimens, but with difficulty and in- 
distinctly, in one or two other directions whose relative incli- 
nation we have not been able to determine. The fracture is 
uneven, glimmering, slightly conchoidal, and vitreous. Some- 
times imperfect prisms are partially united together ; not 
however in the decided and delicate manner of the pycnite ; 
in other cases the mineral consists of a solid irregular mass 
several inches in diameter, exhibiting however when broken 
the foliated structure, parallel to the base of the prism, er 
prisms, which are frequently irregularly divided by seams 
filled with thin layers of mica. Crystallized mica usually in- 
vests the crystals, its prisms penetrating the mineral under 
consideration to a considerable depth. The sides of several 
ef the specimens which we have examined are longitudinally 
Striated. The colour of the best characterized specimens 
is honey yellow, sometimes limpid as quartz in small pieces 
andsometimes white. Itis mostly only translucent, resem- 
bling light-coloured feldspar. ue. 
By mere friction it is not perceptibly electric ; but on heat- 
ing it, it becomes decidedly so, and on applying the different 
extremities of a crystal to a suspended magnetic needle, it was 
found to possess polarity. This needle wasused merely as 
a convenient electrometer. 
' The specific gravity, as determined by six trials with differ- 
ent specimens, is as follows : 
Ist trial - . = - 3.44 
a 
Sq: te a us i BI 3.42 
ae (44 a iS S 2 © 3.47 
5th ge Bs 2 Bs re 3.44 
6th is ‘, i a e 573.46 
eee 
Mean S45 
Vor. X!—No, 2. a5 
