CALCITES OF NEW YORK 83 
The marked absence of pyramidal forms in the crystal habit and the presence 
of two modifying rhombohedra, entirely absent from the varied types found 
in the later calcite deposition, set it distinctly apart as marking a separate 
genetic phase. At the same time the close association with primary minerals 
which show evidences of corrosion, points to the origin of this type from a 
highly corrosive crystallizing solution, rich in carbonate of lime but still 
far from saturated with silica and iron. 
Type II [pl. 9, fig. 4]. Calcite crystallizing in the forms of type II 
occurs incrusting the surface of joints in the ore body, in’a confused aggre- 
gate of translucent, milky white crystals which exhibit none of the tendency 
toward parallel grouping of separate individuals noticeable in other types 
from this locality. The manner of the crystal massing suggests rapid 
deposition from a solution whose condition of concentration had been influ- 
enced by a sudden cooling, change of pressure or some allied cause. Such 
a change of condition of concentration seems highly probable in the case 
of an open joint filled or partly filled with the crystallizing solution which 
from the nature of the case would be far more sensitive to the influence of 
currents. 
The crystals of this type which average 7 millimeters in diameter, are 
rhombohedral in habit and composed of “ built up ”’ forms, the predominat- 
ing negative rhombohedron being deeply grooved by incipient modifications 
parallel to (0001) and (0112). The rhombohedron Y. (0.19.19.13) is present 
as a series of moderately brilliant but somewhat rounded faces; the form 
was determined by averaging the readings taken on 20 of the best crystals 
available. . The scalenohedron q: (2461) is present, beveling the basal edges 
of the predominating rhombohedron. Indications pointed to a second 
scalenohedron in this zone giving the indexes (10.16.26.3) and beveling the 
basal edges of q: as thin lines from which measurements were obtained with 
great difficulty. The form must be regarded as doubtful. 
Type III [pl. 9, fig. 5; pl. 10]. Calcite crystallizing in forms of this 
type differs from those previously described both in mode of occur- 
rence and habit. They occur for the most part embedded in masses of bys- 
