380 DOMAIN V. CALCAREOUS. 



MODE I. MARBLE. 



Characters. Texture, large or small grained, generally in. 

 distinct concretions ; sometimes so fine grained 

 as to appear compact, and only distinguishable 

 by its glimmering lustre : admitting a fine polish. 



Hardness, of course marmoric. Fracture, fo- 

 liated. Fragments, amorphous, blunt. 



Weight, granitose. 



Lustre, from glimmering to shining; between 

 pearly and vitreous. Somewhat translucent, but 

 the black only on the edges. 



It chiefly consists of about 50 lime, and 40 

 carbonic acid ; whence it is called by chemists 

 a carbonate of lime. 



The most common colours are white and 

 black -, but the others are so numerous, that they 

 may be best observed in the subsequent enume- 

 rations of various kinds of marble. 



For the geognostic relations of this celebrated 

 rock, the reader is referred to Mode III., where, 

 in treating common limestone, a wider field of 

 observation may be opened. 



Mineralogists have sometimes regarded those 

 marbles as primitive which present what they 

 call a granular fracture, of a shining or saline 



