86 NEW YORK STATE MUSEUM 
differs from those preceding in the much greater development of the planes 
of the negative rhombohedron ¢.(0221), which here amounts to almost a 
rhombohedral habit, and in the presence of the negative rhombohedron 
y. (0554), a form hitherto unnoted in the occurrence. The scalenohedron 
K: (2131) common to the majority of the other crystals of this type is absent 
from this combination. 
Type IV [pl. 11, fig. 1-3]. Figure 1 shows a combination resulting 
from the development of the negative rhombohedron &. (0443) which here 
replaces the planes of the pyramids 1 and ; to the extent of giving to 
crystals of this phase a rhombohedral aspect. The pyramids ; (8.8.16.3) and 
i (2243) which connect this combination with type III are present as faces 
of great brilliancy, as are also the planes of K:(2131). The rhombohedron 
§. (0443) here replaces Y. as a series of brilliant planes which yield excellent 
reflections. Genetically this type corresponds closely with type III, the 
crystals occurring with considerable secondary quartz embedded in chlorite 
also of the second generation. The crystals are clear and faintly yellow 
in color and measure from 6 to 10 millimeters on the vertical axis. 
A curious variation of this type was noted on a large mass of horn- 
blende which was thickly imcrusted with albite crystals.1 These calcite 
crystals were symmetrically disposed in parallel position on the six basal 
angles of a positive rhombohedron p. (1011), the latter evidently of a pre- 
vious growth and considerably etched and roughened on the surface. One 
of these composite crystals is shown in figure 3 and an enlargement of one 
of the superposed secondary crystals in figure 2. The secondary crystals 
of this phase bear a general resemblance to the modified combination of 
type III [pl. 10, fig. 3] in that they show the scalenohedron U(14.12.26.5) 
beveling the alternate polar edges of the prevailing pyramid ;(8.8.16.3). 
The pyramid (1123) in the same series with those previously noted appears 
as a terminal modification consisting of deeply striated faces. The scaleno- 
hedron U: (5491) of type I here reappears for the first time as a series of small 
1 The writer is indebted to Mr H.H. Hindshaw for the loan of this handsome specimea 
as well as for material taken from it for study. 
