PHYSIOGRAPHY. CLASS i|. 



thin to reflect green and red colours, but admit neverthe- 

 less of being measured by means of the reflective gonio- 

 meter. 



3. It occurs in small quantities in veins, traversing pri- 

 mitive or grey wacke rocks, associated with ores of lead and 

 antimony, with dodecahedral Garnet-blende, rhombohedral 

 Lime-haloide, and very often rhombohedral Quartz. 



4. Beautiful, though generally compound varieties of 

 aggregated tabular crystals, have been found at Przibram 

 in Bohemia, prisms of considerable thickness at Braunsdorf 

 in Saxony. It is found also at Malaczka in Hungary, in 

 Baden, in Nassau, and at Allemont in Dauphiny. 



ORDER III. KERATE. 



I. PEARL-KERATE. 



1. HEXAHEDRAL PEARL-KERATE. 



Hexahedral Corneous Silver. JAM. Syst. Vol. II. p. 350. 

 Man. p. 90. Muriate of Silver. Horn Silver. PHILL. 

 p. 295. Hornerz. WERN. Hoffm. II. B. III. 2. S. 51. 

 Hornsilber. HAUSM. III. p. 1010. Silber-Hornerz. 

 L.EONH. S. 208. Argent muriate. HAIJY. Traite', 

 T. III. p. 418. Tabl. comp. p. 75. Traite, 2de Ed. T. III. 

 p. 292. 



Fundamental form. Hexahedron. Vol.1. Fig. 1. 

 Simple forms. H, Johanngeorgenstadt, Saxony ; 



6, Vol. I. Fig. 2., Siberia; D, Vol. I. Fig. 31. 



Siberia. 



Char, of Comb. Tessular. 



Combinations. 1. H. O. Vol. I. Fig. 3. and 4. 

 Wheal Mexico, Cornwall. 



2. H, D. Fig. 151. Johanngeorgenstadt. 

 Cleavage none. Fracture more or less perfect con- 



phoidal. Surface of the hexahedron sometimes 



