Supposed New Mineral Species. 359 
Figures 1 and 2, however, represent the usual forms of the 
mineral ; and it isa somewhat remarkable circumstance, that it 
appears to be as rare at these localities, under a compound or mas- 
sive form, as it is under regular crystals at Phillipstown and Gren- 
ville. 
Fig. 1. Fig. 2. 
x 
P a 
M a : : ‘ 
a “a j : : ; 137 30 
M “‘e¢ 135 10 
G2 bashes : ices 110 30 
M “ Bb : : ; é 145 00 
Both c 118 00? 
The edges of the civeisin’ are a sharp and well defined. 
The faces also are flat, though considerably pitted, from a natural 
incompleteness in part, but still more from imbedded minerals, as 
apatite, zircon, pyroxene, plumbago, &c. It must not be consid- 
ered, therefore, that the angles above given, will be found inca- 
pable of correction. 'They are, however, the averages of numer- 
ous trials, the limits of variation were generally within 40’. 
_ No very-marked difference in lustre is perceptible on the dis- 
similar faces of the crystals, if sec ag ec and 3, which are both 
inferior to the others in this respect. 
The planes P, ona few of the crystals, exhibit dehcuie lines of 
cleavage in two directions, approaching, but not identical with, 
their edges of intersection with M and M; which cleavage marks 
are likewise visible on the lateral planes, both primary and sec- 
ondary, as denoted in figure 2. The cleavage which takes place 
in conformity with these lines, does not afford a solid of the 
same dimensions with the primary form. Indeed, there is a con- 
stant difference between the two cleavages, as to the facility 
with which they are effected, and the lustre of the resulting 
faces. 'The inclination of the most brilliant cleavage plane to P, 
is between 130° and 131°, while the cleavage prism itself affords 
