14 PHYSIOGRAPHY. 



Limonite. 



constituting sub-species, notwithstanding the close connexion of these 

 varieties thus distinguished, by immediate inter-transitions. In the first 

 place, some of what are generally regarded as pseudomorphoses, or sup- 

 posititious crystals, must be excluded, because they are not real pseudo- 

 morphoses, consisting of compound varieties of this species, but are de- 

 composed varieties of three others, viz. Iron Pyrites, White Iron Pyrites 

 and Spathic Iron, to which they must be severally referred. The 

 fibrous Limonite, or Brown Hematite, contains the real crystals, 

 and the compound varieties in stalactitic, reniform, and other imitative 

 shapes ; also those massive varieties in which the composition may still 

 be ascertained. A crystallized variety, in thin laminae, has been called 

 Rubinglimmer or Gothite. Compact Brown Iron-Ore comprehends 

 those imitative shapes and massive varieties, in which the composition is 

 no longer observable, but which are still firmly connected ; while Ochrey 

 Brown Iron-Ore is applied to those which have an earthy texture, and 

 are friable. As impure varieties of this species, or those in which other 

 species are mechanically blended, we must consider some of the clay 

 Iron-Ores, such as the Granular, the Common, the Pisiform, and the 

 Reniform clay iron-ore. The granular variety is composed of compact 

 roundish or globular masses ; the reniform ore, of alternating coats of 

 different color and consistency, disposed in a reniform surface. In the 

 pisiform variety, we meet with a similar composition, only in small glob- 

 ules, parallel to the surface of which the laminae are disposed. The com- 

 pact pisiform clay iron-ore, however, does riot belong to the present spe- 

 cies, but it is a decomposed White Iron Pyrites, as is proved not only by 

 the crystalline forms which it presents, and which are described in 

 books, but likewise from the nucleus of undecomposed pyrites, which 

 larger specimens of it often contain. To this species also appear to be- 

 long several scaly and nearly impalpable varieties of Iron-Ore, as the 

 Lepidpkrokite, Pyrrhosiderite, and Sideroschisolite ; though it is probable 

 that some of them contain scales of Specular Iron also. 



2. Before the blow-pipe, it becomes black and magnetic. It melts 

 with boi'ax, into a green or yellow glass, and is soluble in heated nitro- 

 muiiatic acid. 3. Analysis. 



By D'AuBuissoN. 



A fibrous variety. A compact variety. 



Peroxide of iron . 82-00 . . 84-00 



Water . 14-00 . . . n-QO 



Oxide of manganese . 2-00 . . . 2-00 



Silica . 1-00 . . . 2-00 



