LIME. 



223 



Fig. 80. 



Rensselaer Couxtv. Crystals assuming tlic lenticular form, but of small size, have been 

 found in fissures in the rork, near Troy. 



Rockland County. The excavations for the New-York and Eric 

 railroad at Piermont, have exposed veins of trapj)ean minerals of seve- 

 ral kinds. Associated with these are found minute crystals of calca- 

 reous spar, which sometimes have the form of the scalene dodecahe- 

 dron ; and at others, nearly approach the cube, cubo'ide of Haiiy. Fig. 

 80. h on h 87^ 48' ; /* on h' 92° 12'. In my specimens, these crystals 

 are associated with stilbite. 



At Tompkins' limestone quarry near Caldwell, several very inte- 

 resting forms of calcareous spar have recently been found. Indeed 

 this promises to become one of our most important localities. The 

 crystals are often doubly terminated, and vary in size from being 

 minute, to two or three inches in length. They are often highly finished and perfect ; most 

 commonly, however, they are grouped, and exhibit only a single termination. The colours 

 are white and yellowish ; translucent to opaque. The forms which I have observed are the 



F.g. 83. 



Fig. 81. 



hinaire of Hauy (Fig. C9) ; the modification. Fig. 81 ; the doducaedre of Haiiy (Fig. 62) ; the 

 same with the edges replaced at the upper part by triangular planes, Fig. 82 ; the mrtastatiquc 

 of Haiiy (Fig. 60), and a modification similar to Fig. 78 ; together with a twin of the same, 

 Fig. 83. The terminal planes of Figs. 62 and 82 often have a convex form, which extends 

 also to the sides of the prisms ; it is hence very difficult to determine the exact value of the 

 replacing planes. 



To the above may be added the following, which have also been found at this locahty : 



