PHYSIOGRAPHY. 127 



Py roln site. 



Rather sectile. Hardness = 2'0 .. .2*5. Sp. gr. = 

 4*94, from Elgersburg ; 4-819. TURNER. 



Compound Varieties. Reniform coats. Both colum- 

 nar and granular composition is often met with, particularly 

 the former ; the individuals often radiating from common 

 centres. If the individuals are very delicate, the masses 

 will soil the fingers, and write on paper. 



1. Before the blow-pipe, it gives the customary reaction of manga- 

 nese-ores. 



2. Analysis. 



By TURNER. 



Red oxide of manganese . . . . . 85-617 



Oxygen 11-599 



Water . . . . . . . 1-566 



Silica . . . . . . . 0-553 



Baryta 0-665 



Lime ....... a trace. 



3. Pyrolusite is very often the product of decomposition from Spathic 

 Iron, the carbonate of iron of the latter being converted by natural 

 agents, into the hydrate of the peroxide, while the lime, which it occa- 

 sionally contains, is deposited in the shape of Calcareous Spar, or Arrag- 

 onite ; and the Manganese is often found covering the surface of decom- 

 posed rhomboids of the original species, in the shape of minute crystals. 

 In this manner, it occurs in the mines of decomposed Spathic Iron, in 

 beds in gneiss, at Hiittenberg in Carinthia, at Schwalkalden in Hessia, 

 and other places. It is likewise found in this manner in the counties of 

 Sayn, Siegen, Salm, and Hamm in Prussia, in the veins of Spathic Iron 

 traversing clay slate, which are decomposed in the upper levels, and 

 then contain much Limonite. One of the varieties from Horhau- 

 sen is particularly remarkable for the delicacy of the fibres, which 

 are disposed in small tufts, within the geodes of Limonite, and which 

 greatly resemble the fibrous varieties of Grey Antimony. Weyer in the 

 county of Wied-Runkel, Hirschberg near Ahrensberg and Beodorf on 

 the Lower Rhine, are likewise quoted as localities of superb specimens 

 of Pyrolusite. The finest crystals of Pyrolusite, occur at Schimmel and 

 Oslerfreude near Johanngeorgenstadt, and at Hirschberg in Westphalia. 

 These are chiefly short thick prisms, terminated on their extremities in 



