146 On Calderitey a new Rock from Burdwan. [No. 2. 



Description. 



This rock can be in no way so well described as by saying, at once, 

 that while on the weathered surfaces it resembles a common massive 

 ore of iron, its appearance on the fresh fracture is exactly that of black 

 rosin. When examined by the magnifier it is seen to have a golden 

 resinous (which is a yellow quartzy) coating, in thin laminae, especially 

 on some of the fractures. On others it has small specks which are 

 seen by the magnifier to be minute cavities full of a yellow powder. 



The fracture is difficult to describe, being in some places hackly, in 

 others tending to small conchoidal, and in some instances breaking on 

 a large scale into an obliquely rhomboidal cavity, as if the rock would 

 cleave naturally into oblique rhomboidal prisms, or contained crystals 

 of that shape. The most perfect cavity I could measure, for I could 

 not obtain a good solid angle, was one of 124° , giving therefore 56° for 

 the acute angle of the rhomboidal crystal. 



The splinters are often nearly laminar and sometimes highly trans- 

 lucent like dark brown rosin. When held to the light, these are seen 

 to contain, here and there, fragments of bright white quartz. 



The streak is ash-coloured, and obtained only with the file, or on a 

 salient edge by the knife. It is brittle and easily fractured with a mo- 

 derate blow. The powder is fawn-coloured. 



When breathed upon it gives a metallic odour. 



The latter portions are tough and difficult to pulverise, requiring 

 repeated sifting and hard pounding. 



Its hardness is 7-8. The specific gravity 3.65. 



The solid mineral does not alter by digestion in acids, and even in 

 Nitro Hydrochloric Acid ; Hydrochloric Acid dissolves a little iron, 

 but in very small proportion (probably from dust) even from extremely 

 thin pieces. 



Before the Blowpipe. 



It fuses in thin fragments at the edges into a black, dull, pitchy, slag, 

 which is magnetic, the siliceous part remaining in the slag. 



With borax the powder fuses immediately into a dark green glass. 



With soda and saltpetre upon platina foil, it gives the usual green 

 mass of manganate of soda. 



