OilDEH vi. PRISMATIC DISTHENE-SPAR. 



niination of the species which it comprehends. The opi- 

 nions of mineralogists have been much at variance in 

 regard to these substances ; but generally they have 

 placed them near each other in their systems, on account 

 of their close resemblance, upon which depends the deter- 

 mination of the genus. A more accurate examination 

 of their forms will remove in future every doubt on 

 the determination of the species, and then only will it 

 be possible to adapt the systematic nomenclature to the 

 geometrical properties of the species, which always must 

 correspond to the state of our information. Mr HAI- 

 DIJTGER has shewn, (Trans, of the Royal Soc. of Edinb. 

 VoL X. p. 127.) that one of the formerly supposed spe- 

 cies of the present genus, the Green Diallage of HAUY, 

 contains nothing but varieties of two other species, the 

 hemi-prismatic and paratomous Augite-spar, either pure 

 or variously blended with each other. An exact com- 

 parison of several varieties of the remaining species with 

 the same two species of the genus Augite-spar, with which 

 they agree so nearly in many of their properties, will af- 

 ford in future an excellent test for the correctness of their 

 determination. 



GENUS II. DISTHENE-SPAR. 

 1. PRISMATIC DISTHENE-SPAR. 



Prismatic Kyanite. JAM. Syst Vol. II. p. 94. Man. 

 p. 134. Kyanite. Cyanite. PHILL. p. 81. Cyanit. 

 Rhaetizit. WERN. Hoffm. H. B. II. 2. S. 313. IV. 2. 

 S. 128. Kyanit. HAUSM. II. S. 636. Disthen. 

 LEONH. S. 422. Disthene. HAUY. Traite', T. III. 

 p. 220. Tabl. comp. p. 54. Traite', 2de Ed. T. II. 

 p. 357. 



Fundamental form. Scalene four-sided pyramid of 

 unknown dimensions, the axis of which is in- 

 clined in the planes of both diagonals. Vol, I. 

 Fig. 42, 



