PHYSIOGRAPHY. 



It is infusible before the blowpipe. If digested in acids, 

 it becomes friable and gelatinous. It consists, according 

 to CHENEVIX, of 



Silica 42-50. 



Alumina 37'50. 



Lime 15-00. 



Oxide of Iron 3-00. 

 and a trace of Oxide of Manganese. 



It occurs in the Carnatic, imbedded in prismatic Feld-spar, 

 and accompanied by rhombohedral Corundum, dodecahedral 

 Garnet, hemi-prismatic and prismatoidal Augite-spar. In- 

 dianite is not a well defined species. Mr BROOKE observes, 

 that the angle of its cleavage planes is that of silicate of 

 lime (prismatic Augite-spar). It is supposed by BEUDANT 

 to be a variety of Labrador! te. 



IRIDIUM, 



METAL. 



Iridium. JAM. Syst. Vol. III. p. 54. Alloy of Iridium 

 and Osmium. PHILL. p. 326. 



Rhombohedral. Six-sided prisms, combined in paral- 

 lel position with two isosceles six-sided pyramids, 

 having bases of 110 36' and 130 6'. BOURNON. 

 Cleavage perpendicular to the axis. Grains. 



Lustre metallic. Colour pale steel-grey. Opake. 



Brittle. Harder than native Platina, Sp. Gr. = 19-5, 

 WOLLASTON. 



If melted with nitre it becomes black ; but again ac- 

 quires both its colour and lustre, if heated with charcoal. 

 It is not dissolved by nitro-muriatic acid. It is an alloy 

 of iridium and osmium, and is found in South America 

 with native Platina. It was first described by Dr 



LASTONV 



