60 



GEOLOGY OF THE SECOND DISTRICT. 



and a half liigh. Other masses, near Muscolunge lake, are composed of about half mica, 

 ill small but very perfect crystals in six-sided tables : they are disseminated very equally 

 tlurough the rock. In Chester in WaiTen coimty, mica forms a compound rock whh carbonate 

 of lime, but is separated more into seams. The color of this mica is an olive gieen, and the 

 complexion of tlic rock is very similar to granite. 



It is scarcely necessary to attempt to describe all the varieties produced by intermixture of 

 these two simple minerals ; they are quite numerous ; as rocks they are unimportant ; but 

 taken in connection with the origin of hmestone, these varieties favor very materially the views 

 which have been supported in the preceding pages. We see in those compounds the most 

 perfect analogy preserved between this rock and granite ; especially when taken in connection 

 with the fact that the common grey quartz forms a constituent of the rock at many places, 

 though it is not so constant as mica ; and perhaps it would have been more agreeable to fact, to 

 have spoken of it under the name of carbonate of lime, mica and quartz. 



2. Carbonate of Lime and Serpentine. This compound rock is scarcely less important than 

 primitive limestone itself. It will be impossible, however, to speak of the numerous varieties 

 which arc common in the northern counties. A few will suffice : 



1. We meet with these two minerals combined in the rock in about equal proportions. The 

 limestone is grey or milk white : the serpentine is always some shade of green ; pale, or 

 yellowish green, is the most common. Large masses are often seen, compact, translucent, 

 and susceptible of a fine polish. 



2. An interesting variety is abundant in Warrensburgh. It contains agatized balls, or oval 

 masses, in which the arrangement of the serpentine and limestone is rudely similar to agate. 

 The annexed cut No. 19 represents this variety. The central portion seems to be a much 



19. 



harder substance than the serpentine or limestone. By trial, I find it difficult to give a good 

 polish to this variety. Not, however, tliat it is not susceptible of a fine polish, if treated with 

 care ; but where a rock is composed of two or three materials, differing in hardness, the 

 softer wears down more rapidly, and does not appear to be acted upon sufiiciently to give the 

 desired lustre. 



