ON THE PRIMITIVE FORMS OF CRYSTALS. 53 



3. Regular Heooaedral Prism. 

 Emerald. 



Beryl. 



Phosphate of lime. 

 Nepheline. 



Arseniate of Copper. Bournon, Phil. Trans. 



4. Octohedron with a Square Base. 

 Zircon. 



Mellite. 



Molybdate of lead. 



Oxide of tin. Philips, Geolog. Trans. 



Octokedrite. 



Tungstate of lime. 



5. Bipyramidal Dodecahedron. 

 Quartz. 



Phosphate of lead. 



IlD CLASS OF PRIMITIVE FORMS. 



CRYSTALS WITH TWO AXES. 



1. Right Quadrangular Prism, — Base a Square. 

 Sulphate of magnesia. 

 Chromate of lead. 

 Mesotype. 

 Nadelstein. 



Sulphate of zinc. Bournon, Cat. p. 185. ' 

 Prussiate of potash. Bournon, Cat. p. 181. 

 Muriate of barytes. Bournon, Cat. p. 187. 



