Mineralogy of New York. 35 



veins of dull white grayish and greenish colors. It is infusible 

 except on the thinnest edges, which become rounded and the 

 color of the mass lighter. Prof. B. suggests the name Rockland- 

 ite for this mineral, if received as a new species. 



Hornblende, Pyroxene. — A large number of interesting locali- 

 ties of these species are given by Prof. Beck. We refer to his 

 work for them, and notice here only one or two hornblende 

 pseudomorphs. One from Warwick, having the form and cleav- 

 age of hornblende, resembles steatite in feel and hardness. The 

 crystals are six-sided prisms with dihedral summits, and are some- 

 times bent and distorted. Prof. Beck found them to consist of sili- 

 ca 35-00, alumina 32.33, lime 10.80, magnesia 20.70. They oc- 

 cur in limestone with mica, fluor and chondrodite. These crystals 

 are "probably hornblende altered by an intrusion of alumina and 

 a removal of part of the silica. The contorted and somewhat 

 fused appearance of many of the crystals clearly point to heat as 

 the agent by which these changes have been produced." Prof. B. 

 asks, " may not the chondrodite have been formed by the combi- 

 nation of the silica which these crystals have lost, and the fluor 

 from the decomposition of the mica ?" mica having also contri- 

 buted, as he before suggested, to furnish the additional alumina. 



Another pseudomorph in long rhombic prisms with the angles 

 of hornblende, and presenting a grayish green color, with the 

 softness of talc, afforded Prof. B. silica 34-66, alumina 25-33, 

 lime 509, magnesia 25-22, water 909. 



Hypersthene. — Prof. Beck finds on analysis, that the hyper- 

 sthene of northern New York, differs little in composition from 

 common pyroxene. He obtained for a specimen from near Ti- 

 conderoga, silica 45-45, lime 24-33, magnesia 1800, oxyd of 

 iron 11.49. 



Idocrase. — The xanthite of Warwick, has the crystalline form 

 and composition of idocrase, and there is no doubt of the identity. 



Feldspar and scapolite occur under a great variety of forms 

 and in crystals of unusual dimensions ; but we pass on, referring 

 for an account of them to Prof. Beck's work. 



Stellite. — The mineral from Bergen Hill, supposed to be the 

 same with Thomson's stellite,% consists according to Prof. B. of 

 silica 54-60, lime 33-65, magnesia 6-SO, oxyd of iron and a little 

 alumina 0-50, water and carbonic acid 3-20.* 



* See Dr. Beck's article on the minerals of Bergen Hill, in this Journal, Vol. 

 xliv, p. 54. 



