Natural History, — Mineralogy. 197 
The most remarkable differences are contained in the follow- 
ing Table : — 
Forms in General, 
Felspar. 
Albite. 
Labradorite. 
Anorthite. 
Bino-unitary. — 
Weiss. 
Hemi-prismatic. 
— itfoAs. 
Unitary. Weiss. 
Tetarto-prisma- 
tic — Mohs. 
Unitary. Weiss, 
Tetarto-prisma- 
tic. — Mohs. 
Unitary. Weiss. 
Tetarto-prisma- 
tic. — Mohs. 
Measures of the principal Angles, referring to the figures f 
Felspar. 
Albite, 
Labradorite 
Anorthite. 
P to M, 
90° 0' 
93° 36' 
Nearly 93-1° 
94° 12' 
P to /, 
112 1 
110 51 
— 
— 
P to T, 
112 ] 
115 5 
— 
110 57 
1 to M, 
120 
119 52 

122 2 
T to 
120 
122 15 
— 
120 30 
j T to M, 
120 
117 53 
— 
117 28 
! 
Weiss. 
Fose, 
Rose. 
Rose.' 
Specific Gravity according to Rose. 
Felspar. 
Albite. 
Labradorite. 
Anorthite. 
From 2.394, 
To 2.581. 
From 2.608, 
To 2.619. 
From 2.695, 
To 2.7025. 
From 2.656, 
To - 2.763. 
Chemical Characters calculated according to Formulae established 
by experiment. 
Felspar. 
Albite. 
Labradorite 
from La- 
brador, by 
Klaproth. 
Anorthite 
from Monte 
Somma, bV 
Rose. 
Silica, 
65,94 
69,78 
55,75 
44.49 
Alumina, - 
17,75 
18,79 
26,50 
34,46 
Potash, 
16,31 
— 
— 
— 
Soda, 
— 
11,43 
4, 
— 
Lime, 
. 
— 
n, 
15,68 
Oxide of Iron, 
— 

1,25 
0,74 
Water, 
— 
— 
0,50 
— 
Magnesia, 
— 
— 

5,26 
' 
100.00 . 
100,00 
99,00 
100,63 
Mr Rose has given the following chemical formulae along with 
the analyses. 
