120 NEW YORK STATE MUSEUM 
The crystals which average 5 millimeters in diameter are colorless 
and transparent. They are rhombohedral in habit, having for dominant 
form the fundamental rhombohedron p.(1011). The rare scalenohedron 
M: (16.4.20.3) in the zone [4041.1120] is present as a series of small bright 
planes giving good reflections. This scalenohedron which was first noted 
by Sachs' on the calcite from Tharandt lies close to the scalenohedrons 
v (10.3.13.2) from Austin’s glen and %: (11.3.14.2) from Alsen, the former 
of which forms also occurs on the calcite crystals from the Helderberg 
limestone at localities not widely separated from Hudson. The prism 
a (1120) is present in relatively small development. 
SUMMARY OF MEASURED AND CALCULATED ANGLES 
LETTER ANGLE RCE MEASUR ALCUL 
RB AMENES EASURED | CALCULATED 
(eo) / fo) 7 
Me: + Me: 16.4.20.3 :16.20.4.3 i 96 15 S6 264 
Me: : Me: 16.4.20.3 e 20) 46. 16.83 6 Pall 31 Pall 30 
Mi: : Me: GHA ONS eal Gm Oe 3 42 24 42 27 
RONDOUT, ULSTER CO. 
Plates 25-27 
The vein calcite of Rondout occurs, for the most part, as a secondary 
deposit on dolomite and presents types of crystallization of marked variety 
and unique development. The associated pyrite which is here present in 
extremely minute crystals, occurs in many cases included in the larger 
calcite individuals arranged along the crystallogenetic lines of the latter 
mineral in distinct bands on the surface of, or as phantoms within, the 
crystals of the calcite. These structure lines as outlined by the pyrite 
inclusions are of notable interest in their relation to the development of 
the calcite. Somewhat similar inclusions have been noted in the calcite 
from Phoenixville, Pa. 
Sachs, A. Zeitschr £ Kryst. 1902) 36:449: 
