VI. INTRODUCTION. 



The composition of the Stratified fossiliferous rocks may 

 be stated generally, as consisting of Argillaceous, Cal- 

 careous, or Siliceous masses, as Clay, Lime or Silex, form 

 their chief proportions. The Unstratified rocks are far 

 more variable in their composition, as numerous other 

 mineral bodies constitute their component parts, or fre- 

 quently occiu" in them, of which the minerals in the sub- 

 joined list are among the principal, and as some vary in 

 their external characters, the Student should be provided 

 with several varieties, to illustrate the crystalline form, 

 fracture, and colour, or other physical characters. 



Siliceous Minerals. Zeolitic Minerals, 



Chiefly found in Amygdaloid Rocks in tlie 

 Rock Crystal, hexagonal prism. western parts of Scotland, Giant's Causeway 



Rock Crystal, with conchoidal ApophyUite. 



fracture. Analcime. 



Quartz crystallized. Brewsterite. 



Violet Quartz, or Amethyst. Chabasie. 



Yellow Quartz Cairngorum. Gmelinite. 



Brown Quartz. Harmotome. 



Rose Quartz. Heulandite. 



Ferruginous Quartz. Laumonite. 



Arenaceous Quartz, Sand. Mesole. 



Arenaceous Quartz, coloured by Mesotype. 



oxides of Iron. Natrolite. 



Opal. Phillipsite. 



Semi-Opal. Prehnite. 



Wood Opal. Stilbite. 



Calcedony. Thomsonite. 

 Agate, from Amygdaloid rocks. Clays. 



Agate, enclosing fossil sponge, &c. Slate Clay, Shale. 



Flint. Bituminous Shale. 



Hornstone. Rotten-stone. 



Jasper. Adhesive slate. 



Porcelain Jasper. Fuller's Earth. 



