250 PHYSIOGRAPHY". CLASS II. 



GENUS VII. FELD-SPAR. 

 1. RIIOMBOHEDRAL FELD-SPAR. 



llhomboldal Felspar or Nepheline. JAM. Syst. Vol. II. 

 p. 40. Man. p. 153. Sommite. PHILL. p. 125. Ne. 

 phelin. WERN. Hoffm. H. B. II. 1. S. 365. Nephe- 

 lin. HAUSM. II. S. 552. Nephelin. LEONH. S. 417. 

 Nepheline. HAUY. Traite', T. III. p. 18G. Tabl. corap. 

 p. 51. Traite', 2de Ed. T. III. p. 347. 



Fundamental form. Rhomb ohedron. R = 83 5'. 

 Vol.1. Fig. 7. AP. 



Simple forms. R oo(P); R+OD; P(r) = 139 



19', 88 6'; P + 1 = 127 16', 125 30'; 



P + oo (M). 



Char, of Comb. Di-rhombohedral. 

 Combinations. 1. R oo. P 4- oo. Vesuvius. 



2. R oo. P. P + oo. Fig. 112. 

 Cleavage, R oo and P -f oo, both imperfect. 



Fracture conchoidal. Surface smooth and even. 

 Lustre vitreous. Colour white. Streak white. 



Transparent ... translucent. 

 Brittle. Hardness = 6-0. Sp. Gr. = 2-560. 



Compound Varieties. Massive : composition 

 granular, of various sizes of individuals. Faces of 

 composition rather rough. 



OBSERVATIONS. 



1. Two analyses, 1. by VAUQUELIN, of a variety from 

 Monte Somma, 2. by CARPI, of a variety from Capo di 

 Bove, have yielded : 



Alumina 1. 49-00 2. 9-00. 



Silica 46-00 40-20. 



