100 Dr. Turner's Chemical Examination 



must be regarded rather as accidental than essential to the 

 mixture, it follows that braunite is an anhydrous deutoxide of 

 manganese. I apprehend the baryta must be in combination 

 with deutoxide of manganese ; since, were it united with per- 

 oxide, the loss in oxygen would exceed the quantity above 

 stated. 



I am not acquainted with any analysis of this mineral by 

 other chemists. 



Analysis of the Pyramidal Manganese-ore or Hausmannite. — 

 Hausmannite, before being washed, yields a faint odour of 

 chlorine by the action of sulphuric acid. When heated to 

 redness it gives off 0*435 per cent of water ; and at a white 

 heat the loss is only 0*65 per cent, indicating 0*2 1 5 of oxygen. 

 When dissolved in muriatic acid, a small quantity of silica is 

 left, amounting to 0*337 per cent ; and on adding sulphuric 

 acid to the solution, a little sulphate of baryta subsides, indi- 

 cating 0*11 1 per cent of the pure earth. Hausmannite is ac- 

 cordingly resolved by this analysis into 



Red oxide 98*098 



Oxygen 0*21 5 



Water 0*435 



Baryta 0*111 



Silica 0*337 



100*000 

 This oxide is manifestly an anhydrous red oxide of manga- 

 nese. The small quantity of oxygen lost at a white heat is 

 probably owing to the admixture of a little deutoxide or per- 

 oxide, combined with the baryta. 



From some preliminary experiments on hausmannite, M. 

 Gmelin of Heidelberg * inferred that it is a pretty pure red 

 oxide, an inference which entirely agrees with the result of 

 the preceding analysis. This is the only chemical examination 

 of hausmannite by other chemists, which I have met with. 

 The material for my analysis was part of a specimen from 

 Ihlefeld, for which I am indebted to the kindness of Professor 

 Stromeyer. 



Analysis of Pyrolusite, or the Prismatic Manganese-ore, — 

 The following analysis was made with a compact columnar 

 variety from Elgersburg, which has a specific gravity of 4*94, 

 and the individuals of which have a parallel direction. With 

 sulphuric acid it does not yield a trace of chlorine; and 

 the only impurities which I could discover in it are silica and 

 baryta, the former amounting to 0*513, and the latter to 0*532 

 per cent. 



* Lconhard's Handbuch der Orylrtognosia. 



The 



