408 PHYSIOGRAPHY. 



CLASS II. 



caceous Specular Iron-Ore, while the rest form the Common 

 Specular Iron-Ore. Those varieties which have lost the 

 metallic appearance are included within the lied Iron-Ore, 

 divided into Fibrous Red Iron-Ore or Red Hematite, which 

 occurs in reniform and other imitative shapes, and consists 

 of columnar particles of composition ; into Compact and 

 Ochrey Red Iron-Ore, which are massive, and consist of 

 impalpable granular individuals more or less firmly con- 

 nected; and into Scaly Red Iron-ore, or Red Iron Froth, con- 

 sisting of very small scaly lamellar particles, which in most 

 cases are but slightly coherent. This variety is in imme- 

 diate connexion with the micaceous specular iron-ore, and 

 an uninterrupted transition exists between it and the crys- 

 tallised specular iron-ore itself. Among the varieties of Clay 

 Iron-Ore, the following may be considered as an appendix to 

 the present species, all of which are of a red colour, but more 

 or less impure, and mixed with earthy substances. Reddle 

 possesses an earthy, coarse slaty fracture ; it soils and writes, 

 and may be used as a drawing material. Jaspery Clay Iron- 

 Ore has an even, or large and flat conchoidal fracture, and 

 a hardness which is considerable if compared with other 

 minerals of a similar formation. Columnar and Lenticular 

 Clay Iron-Ore are distinguished, the first by the columnar 

 form, the latter by the flattish granular form of its particles 

 of composition. 



2. The micaceous specular iron-ore, analysed by Bu- 

 CHOLZ, and the red hematite, analysed by D'AUBUISSON, 

 have been found to consist of 



Peroxide of Iron 100-00 90-00 ... 94-00. 



Oxide of Manganese 0-00 a trace. 



Silica . 0-00 2-00. 



Lime 0-00 a trace 1-00. 



Water 0-00 2-00 ... 3-00. 



Its chemical sign is Fe, the proportion of metal to that of 

 oxygen being = 69-34 : 30-66. The clay iron-ores, being 

 more or less mixed with earthy substances, vary in their 

 contents, and several of their properties are dependent upon 



