36 PHYSIOGRAPHY. CLASS 1. 



is an object of commerce, is extracted from heaps, gather- 

 ed together for that purpose. 



GENUS IV. ROCK-SALT. 

 1. HEXAHEDRAt ROCK-SALT. 



Hexahedral Rock-Salt. JAM. Syst. Vol. III. p. 1. Man. 

 p. 9. Common Salt. PHILL. p. 193. Naturlich 

 Kochsalz. WERN. Hoffm. H. B. Th. III. 1. S. 222. 

 Steinsalz. HAUSM. III. S. 843. Steinsalz. LEONH. 

 S. 619. Soude muriatee. HAU r. Traite', T. II. p. 356. 

 Tabl. comp. p. 20. Traite', 2de. Ed. T. II. p. 191. 



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

 Simple forms. H (P) ; 6 (o) Vol. I. Fig. 2. ; 



D. Vol. I. Fig. 31.; A*. Vol. I. Fig. 32. 

 Character of Combinations. Tessular. 

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



2. H. A. Fig. 152. 



3. H. D. As. 



4. H. O. A*. 



Cleavage^hexahedron, perfect. Dodecahedron, often 

 distinct, though generally only a few faces. 

 Fracture conchoidal. Surface generally smooth ; 

 the faces of the icositetrahedron sometimes rough. 



Lustre vitreous, somewhat inclining to resinous. 

 Colour, generally white, passing into yellow, 

 flesh-red and ash-grey. Sometimes beautifully 

 violet-, berlin-, or azure-blue. Streak white. If 

 scratched with the nail it does not yield any 

 powder, but receives an impression, and becomes 

 a little shining. Transparent ... translucent. 



Rather brittle. Hardness = 2-0. Sp. Gr. =r 2-257, a 

 yellowish-white transparent variety. Taste saline. 



