OF CENTRAL CANADA PART III. 173 



under No. 82, in Part II), also forms beds among Lauren tian strata,, 

 as in Grenville, Ramsay, and elsewhere. Many deposits of more or 

 less compact soapstone occur likewise in the higher crystalline 

 series of the Eastern Townships, as in various parts of Bolton more 

 especially, and also in Potton, Sutton, Stanstead, Leeds, and Yau_ 

 dreuil. 



Opliiolite or Serpentine Rock : This rock consists essentially of 

 the hydrated magnesian silicate, Serpentine, described fully in Part 

 IF. It usually presents a green, brown, greenish -grey, or pale 

 yellowish colour, often veined or mottled with lines and patches of 

 darker or lighter green, red or reddish brown ; and it forms more or 

 less compact beds, frequently of great extent and thickness. Sub- 

 ordinate examples occur in the Laurentian strata of many localities, 

 mostly associated with bands of crystalline limestone, as in the town- 

 ship of Grenville, and at Calumet Island on the Ottawa ; also in 

 Burgess, and elsewhere ; but the crystalline districts south of the St. 

 Lawrence contain the most abundant and important deposits of ser- 

 pentine rock, as at Mount Albert in Gaspe, and in the Eastern 

 Townships of Melbourne, Oxford, Brougham, Bolton, Ham, and. 

 Garthby, more especially. The serpentine of these districts is very 

 commonly associated with beds of chromic iron ore ; and many ex- 

 amples are intermixed with crystalline calcite or dolomite, forming 

 ornamental " serpentine-marbles " of green, chocolate-brown and 

 other colours. 



Crystalline Limestone : This rock consists of carbonate of lime in/ 

 a crystalline or semi-crystalline condition. It is usually white, light 

 grey, or pale reddish, in colour, and is sometimes veined or spotted 

 with yellow, green, blueish-grey and other tints. It presents most 

 commonly a fine or coarse granular structure, much resembling that 

 of loaf sugar, whence the name " saccharoidal limestone " by which 

 this rock is often known ; but some varieties are more or less com- 

 pact ; and others present in places a fibrous aspect, from inter- 

 mingled tremolite or white hornblende, or light varieties of pyroxene. 

 The finer kinds from the ordinary marbles of commerce. In Canada, 

 large beds of crystalline limestone, often containing scales of graphite,, 

 and crystals of apatite, pyroxene, amphibole, mica and other 

 minerals, occur among the Laurentian and Huroriian series of strata 

 in numerous localities (See Part V) ; and also among the crystalline- 



