106 NEW YORK STATE MUSEUM 
The calcite crystals under consideration occur in vein material in the 
Onondaga limestone associated with saddle-shaped aggregates of dolomite 
and more rarely with crystallized quartz. They represent two generations, 
separated by a period in which dolomite was deposited, of which the older 
consists of brilliant individuals of extremely varied habit which are for the 
most part small, varying from 3 to 10 millimeters in length. One type of 
these crystals of the first generation is represented in figure 1, of the article 
by Penfield and Ford, above cited. . 
The crystals of the second or younger generation are generally larger in 
size than those of older deposition and are largely of scalenohedral type, 
showing a marked tendency to twinning according to several laws. They 
are frequently of a dull surface and black or dark gray in color as the result 
of bituminous inclusions. It is these latter which have been described at 
length by Penfield and Ford. 
The small brilliant crystals of the first generation contain frequent 
inclusions of pyrite, chalcopyrite and marcasite 1n microscopic individuals, 
the latter mineral in beautiful doubly terminated twin crystals, specially 
prevalent in forms of the rhombohedral type. Frequent zones of deposition 
of these inclusions occur which render their aspect almost that of a phantom 
within the crystal. 
First generation 
Type I [pl. 18, fig. 1] Crystals of this’ type which occur im’ the 
lining of a thin seam are characterized by the second order pyramid 
1 (8.8.16.3) developed to a considerable habit. This pyramid is terminated 
by the rhombohedrons p. (1011) and 8. (0112) all of which forms give excel- 
lent reflections. The basal edges of the pyramid are in some instances 
truncated by narrow planes of the prism a (1120), the type gradually merg- 
ing into the combination of type II shown in figure 2. The crystals, which 
are for the most part colorless, transparent and brilliant, are very small, 
the largest not exceeding 4 millimeters in length. 
Type II [pl. 18, fig. 2-4]. Crystals of type II are larger than those 
of the preceding type, averaging 10 millimeters in vertical length. They 
