278 Analysi* of tome Indian Ores of Manganese. 



Hunter has appeared in several of the Madras journals, but 

 as no analysis of it has as yet been published, and as it 

 belongs to a class of manganese minerals of rather rare 

 occurrence, a short notice of it may not be devoid of in- 

 terest. 



It occurs in large irregular masses, some of them described 

 to be of several tons weight. I am not acquainted with the 

 geological formation in which this mineral is met with, never 

 having visited that part of India, but, generally speaking, the 

 prevailing rock in the Indian Peninsula, especially of the 

 Carnatic, in which many minerals containing iron or man- 

 ganese occur, is that which is commonly known by the name 

 of " Laterite," a rock peculiar to that country, and of which 

 an excellent detailed description has been already published 

 by the late Captain Newbold of the Madras army. 



The mineral under consideration presents a highly metallic 

 lustre of a bluish -black colour, interspersed here and there 

 with dull greyish spots, which latter possess the external 

 character of Psilomelan. It breaks with difficulty, and when 

 split with a chisel presents an imperfect rhombohedral clea- 

 vage. Its specific gravity is 4-50. 



Its powder is of a dark brownish-black colour, which dis- 

 solves readily in hydrochloric acid, with the evolution of 

 chlorine gas, and on evaporation forms a gelatinous mass of 

 a deep yellow colour. Its analysis was performed by dis- 

 solving it in hydrochloric acid, evaporating to dryness, and 

 heating strongly, in order to render the silicic acid inso- 

 luble, and effect its separation. The iron was separated from 

 the manganese by succinate of ammonia ; the latter metal 

 being then precipitated by hydrosulphuret of ammonia, was 

 afterwards redissolvecl and thrown down by carbonate of 

 soda, and ultimately reduced to red oxide by subjecting it to 

 a strong heat, in which state its weight was ascertained. 

 The other ingredients were determined in the usual manner. 

 The quantitative constitution of the mineral was found to be 

 as follows : — Silicic acid, 8*300 ; peroxide of iron, 12*910 ; 

 magnesia, 2*339 ; water, 0*539 ; red oxide of manganese, 

 73786 ; oxygen, 1*864 ; total, 99*735. The quantity of me- 

 tallic manganese in the above analysis amounts to 53*428 



