FREE BOOKS

Author's List




PREV.   NEXT  
|<   98   99   100   101   102   103   104   105   106   107   108   109   110   111   112   113   >>  
ng the olivine or chrysoberyl. These are not as frequent as the paler varieties, but when found excite the admiration of visitor and expert. It seems hardly probable that any true emeralds will be uncovered and the yellow beryls may not increase in number. Their use in the arts will be improved by combining them with other stones and by preparing the larger specimens for single stone rings. Very effective combinations of the aquamarine and blue species with the yellow may be recommended. Tourmaline appears in some quantity, forming almost a schist at some points, but no specimens of any value have been extracted, the color being uniformly black. The garnets are large trapezohedral-faced crystals of an intense color, but penetrated with rifts and flaws. Many, no doubt, will afford serviceable gem material, but their resources have not yet been tested by the lapidary. While granite considered as a building stone presents a complex of quartz, mica, and feldspar so confusedly intercrystallized as to make a homogeneous composite, in the present mass, like the larger and similar developments in North Carolina, these elements have excluded each other in their crystallization, and are found as three separate groups only sparingly intermingled. The proportions of the constituent minerals which form granite, according to Prof. Phillips, are twenty parts of potash feldspar (orthoclase), five parts of quartz, and two parts of potash mica (muscovite), and a survey of Mr. Wilson's quarry exhibits these approximate relations with surprising force. There can be but little doubt that this vein is a capital example of hydrothermal fusion, whereby in original gneissic strata, at a moderate temperature and considerable depth, through the action of contained water, with the physical accompaniment of plication, a solution of the country rock has been accomplished. And the cooling and recrystallization has gone on so slowly that the elements of granite have preserved a physical isolation, while the associated silicates formed in the midst of this magma have attained a supremely close and compact texture, owing to the favorable conditions of slow growth giving them gem consistencies. The further development of the vein may reveal interesting facts, and especially the following downward of the rock mass, which we suspect will contract into a narrower vein. At present the order of crystallization and separation of the mineralogical units s
PREV.   NEXT  
|<   98   99   100   101   102   103   104   105   106   107   108   109   110   111   112   113   >>  



Top keywords:
granite
 

physical

 

specimens

 

elements

 

potash

 
crystallization
 
present
 

larger

 
quartz
 

feldspar


yellow

 

surprising

 
downward
 

relations

 
mineralogical
 

capital

 
development
 
hydrothermal
 

reveal

 

approximate


interesting

 

quarry

 

orthoclase

 

narrower

 

twenty

 

Phillips

 

Wilson

 

suspect

 

fusion

 

survey


contract

 
muscovite
 

exhibits

 

original

 

compact

 
recrystallization
 

cooling

 
separation
 

texture

 
accomplished

slowly
 

preserved

 
attained
 
formed
 

silicates

 

isolation

 
favorable
 

conditions

 
temperature
 

considerable