OP.DEH VI. DODECAHEDRAL AZURE -SPAR* 289 



stein. HAUSM. II. S. 543. Lasurstein. LEONH. S. 

 50. Lezulite. HAUY. Traite,T. III. p. 145. Tabl. 

 comp. p. 47. Traite, 2de Ed. T. III. p. 54. 



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

 Simple form. D. Vol. I. Fig. 31. 



Cleavage, dodecahedron imperfect. Fracture im- 

 perfect conchoidal, uneven. Surface even, 

 though rough. 



Lustre vitreous. Colour various shades of azure- 

 blue. Streak blue, paler than the colour. Trans- 

 lucent, generally only on the edges. 



Brittle. Hardness = 5-5 ... 6-0. Sp. Gr. =2-959, 

 KARST^N; = 2-3 ... 2-4, BREITHAUPT. 



Compound Varieties. Massive: composition 

 granular, individuals strongly connected ; fracture 

 uneven. 



OBSERVATIONS. 



1. The difference in the two preceding statements of the 

 specific gravity shews that the present place of the species 

 cannot yet be considered as definitively settled. 



2. Dodecahedral Azure-spar consists, according to GME- 

 LIN, of 



Silica 49-00. 



Magnesia 2-00. 



Alumina 11-00. 



Lime 16-00. 



Potash and Soda 8-00. 



Oxide of Iron 4-00. 



Sulphuric Acid 2-00., 



with a trace of water and hydro-sulphuric acid. Be- 

 fore the blowpipe it melts with difficulty into a glassy 

 globule, which is first of a blueish tinge, but soon becomes 



VOL II. T 



