48 PHYSIOGRAPHY. CLASS I, 



GENUS VII. EPSOM-SALT. 

 1. PRISMATIC EPSOM-SALT. 



Prismatic Epsom-Salt. JAM. Syst. Vol. III. p. 24. Man. 

 p. 16. Sulphate of Magnesia. PHILLIPS, p. 180. Na- 

 turlich Bitter-Salz. WERN. Hoffiu. H. B. Vol. III. 

 1. S. 243. Bittersalz. HAUSM. III. S. 818. Bitter- 

 salz. LEONH. S. 507- Magnesie sulfatee. HAU Y. Traite, 

 T. II. p. 331. Tabl. comp. p. 15. Traite', 2de Ed. 

 T. II. p. 51. 



Fundamental form. Scalene four-sided pyramid. 

 P = 127 22' ; 126 48' ; 78 7. Vol. I. Fig. 9. 

 R. G. 



a : b : c = 1 : V 3 ' 0635 : V 3 ' 0066 - 



Simple forms. P (/) ; P + oo (M ) = 90 38' ; 



'; ?r+oc(o); 



Char, of Comb. Hemi-prismatic, of inclined faces. 

 Combinations. 1. P. P -f oo. 



2. P. P + <z>. IPr + oo. Fig. 6. 



3. Pr. Pr. P. P + oo. Pr -f- oo. 



4. Pr. P. P + oo. (?r + oo) 3 . r + oo. 

 Cleavage, Pr + oo highly perfect; Pr, less dis- 



tinct; traces of P -|- oo. Fracture conchoidal. 



Surface. P + oo sometimes, Pr + oo almost al- 



ways vertically streaked. The rest of the faces 



smooth and even. 

 Lustre vitreous. Colour white. Streak white. 



Transparent ... translucent. 



Rather brittle. Hardness = 2-0 ... 2-5. Sp. Gr. 

 = 1*751. Taste saline and bitter. 



Compound Varieties. Botryoidal, reniform, and 

 in the shape of crusts : composition columnar, if 



