102 NEW YORK STATE MUSEUM 
In the rhombohedral zone the dominant form is the positive rhombo- 
hedron p. (1011) developed as a series of dull planes. The negative rhombo- 
hedron . (0112) is present in considerable development, the planes being 
somewhat rounded and striated in the zone [1011.1120]. The positive 
rhombohedron m. (4041) is present in very small development but yielding 
good reflections. A vicinal rounding was noted between the planes of 
s. (13.0.13.1) and b (1010) the latter of which is often ill defined, the form 
being mainly identified by its position in the prismatic zone. On one crystal 
a single plane of the negative rhombohedron 7. (0445) was noted; the occur- 
rence of the form must, however, be classed as doubtful. In the prismatic 
zone the persistent and symmetric occurrence of a series of planes between 
b (1010) and a(1120) was noted, the measurements corresponding fairly 
closely to the dihexagonal prism <¢ (3140). The form, however, is in no 
case very well defined and must be regarded as doubtful. 
The positive scalenohedron N: (5382) in the zone [1011.1120] is present 
as a series of narrow bright planes considerably rounded in zone. This 
vicinal rounding interfered somewhat with the determination of the form 
although its presence is beyond question. 
A decided twinning parallel to 6. (0112) is characteristic of these crystals 
as shown in figure 2. 
SUMMARY OF MEASURED AND CALCULATED ANGLES 
ANGLE NO. OF : 2 
READINGS MEASURED |. CALCULATED 
1°) 7 te} , 
3° om. 1012 : 4041 4 Ti cord se eon 58 
Boe S, HOW TISHOF 13) 4 6S: 602054 GS 124 
3. 24. 0112 : 0445 1 he ag AD 2 
a ic 1120 : 3140 9 15° 440 16 6 
N: : NY 5382 : 5832 1 Me 7 4b 
N: : NY 5382 : 8352 1 ete ASE hy SA 46 
a::N: 1120 : 5382 10 18 6 cailuais 4 
