Mr. Phillips's Essai/ on Manganese. 255 



which I expressed to you by letter before the publication of 

 your Essay, as the result of a partial and hasty examination, 

 I am now, after careful experiment, prepared to maintain. 

 I have of course employed in these researches the specimen 

 which you were so kind as to give me; and as it is quite free from 

 foreign matter, except a little silica and copper as you men- 

 tion, I apprehend there can be no doubt of our having operated 

 with the same mineral in its state of greatest purity. 



Before proceedmg to the analysis, I may remark, that part 

 of your mineralogical description is inexact. You state, for 

 instance, that the colour of die Warwickshire manganese is 

 gray, not materially differing from the tint of the well-known 

 crystaUized peroxide ; that it is much harder than that mineral, 

 does not soil the fingers so much, and is lighter in the pro- 

 portion of 4*283 to 4"819. If my recollection serves me, most 

 of these statements were derived from my own letter; and 

 though in reference to part of the Warwickshire manganese 

 they are very near the truth, they are erroneous as applied 

 by you to the whole mineral. The Warwickshire ore, I con- 

 ceive, is not, as you imagine, a new definite compound of oxy- 

 gen and manganese, but a mixture of two well-known oxides, 

 manganite or the hydrated deutoxide, and pyrolusite or the 

 anhydrous peroxide. These oxides are so intimately blended 

 with each other in the Warwickshire manganese, that it is dif- 

 ficult to obtain either in a state of purity. I have succeeded 

 in collecting very pure fragments of manganite ; and though 

 no crystalline figure is discernible, all the other characters 

 agree exacdy with those of pure manganite from Ihlefeld. 

 The cleavage, lustre, hardness, and colour of the powder cor- 

 respond closely, or I may even say exactly : and the specific 

 gravity of the purest and most compact fragments which I have 

 obtained, is ^-SSG ; while that of a perfectly pure crystal of 

 manganite, taken at the same time, is -fSlD. The results of 

 analysis likewise coincide, as the following numbers will show : 



Manganite from the Manganite from 

 Warwick Ore. Ihlefeld. 



Red oxide 86'55 86-85 



Oxygen 3-23 3-05 



Water 10-12 10-10 



100-00 100-00 



The peroxide in the Warwick ore is so intimately mixed 

 with manganite, that I have been unable to eflect a j)f ilect se- 

 paration. That manganite thus pervades the substance of the 

 ore is obvious to the eye, since lamina; of that mineral may be 

 seen in almost every part ; and the presence of two distinct 



compounds 



