Mineralogy of New York. 



33 



quarter to an inch and a half in length and have a lustre between 

 resinous and pearly. 



tStrontianite. — " The Emmonsite of Dr. Thomson is certainly 

 nothing more than a mechanical mixture of carbonate of stron- 

 tian and carbonate of lime." — p. 213. 



Calc Spar. — The Rossie lead mines and other places in the vi- 

 cinity have afforded splendid crystallizations of calc spar. " Crys- 

 tals have been obtained twelve inches in diameter, with all the 

 sides perfect," p. 224 ; one in the cabinet of B. Silliman, Jun. 

 weighs one hundred and sixty five pounds, and although a cleav- 

 age crystal in part is finely modified on several of its angles and 

 edges. Prof. Beck has given a number of the simpler forms from 

 this region. The accompanying figure, (fig. 1,) by the writer, 

 represents one of the more complex, not of unfrequent occurrence. 

 The crystals are very commonly rhombohedrons, with a few planes 

 on the edges and angles. The scalene dodecahedron, simple or 

 modified, is another frequent form. They are often compounded 

 parallel with the terminal plane, and also with a prismatic plane 

 on the lateral angles, and some crystals consist of six individuals 

 thus combined. Crystals are occasionally observed in which the 

 terminal plane of the modified rhombohedron, has been covered 



Fig. 1. Fig. 2. 



a 



with a layer of pyrites, and afterwards built upon by subsequent 

 crystallization, until the rhombohedron was completed and the 

 plane wholly obliterated. The writer is indebted to Prof. Em- 

 mons for the examination of a specimen of this kind. Prismatic 

 specimens are not uncommon in which the terminal pyramid (the 

 primary faces) has been similarly incrusted with pyrites and then 

 covered again with crystallizing lime. Another singular effect 

 of intermitted crystallization is represented in the annexed figure, 

 (fig. 2.) In these crystals, the plane a is bordered by an elevated 

 rim, a twelfth of an inch or so high. The crystal after an inter- 



Vol. xlvi, No. 1.— Oct.-Dec. 1843. 5 



