214 J. D. Dana’s Mineralogical Contributions. 
8. Homeomorphism of Andalusite, Topaz, Staurotide. 
_ T: Tin Staurotide is 128° 42’, in Topaz 124° 19’, and in An- 
dalusite (taking #2 as I), 127°. 28. Compared with Topaz, the 
plane 17 (Px ) of Staurotide is 37, and the plane 17 in Andalusite 
is 27. The axes in this view are as follows: 
Topaz, (Al® Sit. F replacing some O) — a: b : c==0'8989 : 1: 18931 
Andalusite, (AI? Si?) a:b: c=0°9487 : 1 : 20268 
Staurotide, (Al? Si) a:b: c=0-9652 : 1°: 20825 
The species Lievrite has some relations to this group: the 
prism I, referred to the above type, would be ¢. 
9. Discrasite, Witherite, Aragonite, ete. 
Discrasite, Ag? Sb I=119° 59’ O : 13==130° 41’ 
Witherite, Ba 6 I=118° 30’ 
Aragonite, Ca G I=116° 10’ O : 17=180° 50’ 
; 10. Augite and Wollastonite. . 
In volume xv, [2], page 449 of this Journal, the author pointed 
out the fact that Wollastonite, by a change of position from that 
ordinarily taken, and one fully authorized, had nearly the angles 
of Augite, as follows: 
Augite, (Mg, Ga)® Si? Es 287 5? O : 22==131° 17’ C=73° 597 
Wollastonite, Ca? Si? I: I=87° 28’  O: 2i==137° 48’ C=69° 4a’ 
The main difference is in the less length and greater obliquity 
of the vertical axis in Wollastonite, and in the cleavage. The 
axes are: 
Augite, - : : : @:b :c=05412 : 1: 091846 
Wollastonite, = - - ~ a:b: e=04838 21: 089789 . ‘ 
It may be of some interest to observe, that the angle I: I in 
the Augite series is near the rhombohedral angle of the Corun- 
dum series, which varies from 84° to 88°. 
11. Pyrolusite and Gthite not closely homeomorphous. 
The angle I: I of Pyrolusite =93° 40’, and is near the corres- 
ponding angle of Gothite and Diaspore. But O: 42 in Pyrolus 
site is 160°, which gives 143° 57’ for O: 13, and this differs 5 
from the same angle in Gothite. 
12. Homeomorphism of Monazite, Lazulite. 
Monazite (Ge, fa,th)® (I); Wagnerite Mg*P+MgF (11); Lat 
ulite (R+A1)B4+H? (IIL). 
L 1:T=98° 10’; C=76° 14’; O: 101389 87 ..+. a:b :¢ == 0.94715 5 1: 10269 
IL I:1==95° 95/; C=63° 957; O:11=146° 3’.-.a:b:e = 07401 21: 09881 
TIT. 1: 1=919 80’; C=88° 15’; O:17==139° 45’. a:b:¢ = 086904: 1: 10260 
The inclination of the vertical axis (angle C) varies widely; 
and consequently O on the clinodiagonal prism 1i(P/ «) 
