GNEISS MICA SLATE. 353 



Granite is also used for paving, in small rectangular blocks 

 neatly fitted together, as in London and in some parts of 

 New York and other cities. The feldspathic granite is of 

 jgreat value .in the manufacture of porcelain, as remarked 

 upon under Feldspar. 



Granite was much used by the ancients, especially the 

 Egyptians, where are obelisks that have stood the weather 

 for 3000 years. 



GNEISS. 



Gneiss has the same constitution as granite, but the mica 

 is more in layers, and the rock has therefore a stratified ap- 

 pearance. It generally breaks out in slabs a few inches to 

 a foot thick. It is hence much used both as a building ma- 

 terial and for flagging walks. The quarries in the vicinity 

 of Haddam, Conn., on the Connecticut river, are very exten- 

 sively opened, and a large amount of stone is annually taken 

 out and exported to the Atlantic cities, even as far as New 

 Orleans. There are also quarries at Lebanon and other 

 places, in Connecticut; at Wilbraham, Millbury, Monson 

 and many other places in Massachusetts. 



MICA SLATE. 



Mica slate has the constituents of gneiss, but is thin slaty, 

 and breaks with a glistening or shining surface, owing to the 

 large proportion of mica, upon which its foliated structure 

 depends. It contains less feldspar and much more mica 

 than gneiss. 



The thin even slabs of the more compact varieties of mica 

 slate are much used for flagging, and for door and hearth 

 stones ; also for lining furnaces. The finer arenaceous va- 

 rieties make good scythe stones. 



It is quarried extensively of fine quality, in large even 

 slabs, at Bolton in Connecticut ; also in the range passing 

 through Goshen and Chesterfield, Mass. It is worked into 

 whetstones in Enfield, Norwich, and Bellingham, Mass., and 

 extensively at Woonsocket Hill, Smithfield, R. \. The south 

 part of Chester, Vt., affords a slate like that of Bolton. Mica 

 slate is used at Salisbury, Conn., for the inner wall of the 

 iron furnace. 



Hornblende slate resembles mica siate, but has not a« 

 glistening a luster, and seldom breaks into as thin slabs. It 

 is more tough than mica slate, and is an excellent material 

 for flagging. 



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