SILICA GROUP—Continued. 



Quartz fa. Rock Crystal.) — continued. 



Group of pyramids deposited upon others. 

 Do. Large group of prisms, with drusy surfaces. 



Do. Large group of prisms, wich drusy surfaces. 

 Loc, Cornwall. 



Do. {b. enclosing other minerals). — Enclosing oxide of 

 iron. 



Do. Prisms enclosing Rutile and Adularia. 

 Loc, Tintagel. 



Do. Flattened prism enclosing Tourmaline. 



Loc, St. Gothard. 

 Do. Transparent crystal enclosing Rutile. 



Loc, Brazil. 

 Do. Pyramids enclosing scales of Oxide of Iron. 

 Do. Flattened prism enclosing Rutile, &c. 



Do. Transparent crystal enclosing air and water. 

 Loc, Dartmoor. 



Do. Pyramids partially enclosing oxide of Iron. 

 Loc, St. Just. 



Do. Enclosing red oxide of Iron. 

 Loc, Cornwall. 



Do. Flattened prism enclosing Rutile. 



Do. ic. Amethyst). — Large deep purple crystals. 



Do. Group of large crystals. 



Do. Group of semi-transparent crystals. 

 Loc, Cornwall. 



Do. Group of short pyramids. 

 Loc, Cornwall. 



Do. Group of short pyramids. 

 Loc, Cornwall. 



Do. {d. Milk Quartz.) — Massive. 

 Loc, Cornwall. 



Do. (e. Hose Quartz). — Very pale specimen. 

 Loc, Bavaria. 



