PHYSIOGRAPHY. CLASS n. 



OBSERVATIONS. 



1. The division introduced among the varieties of the 

 present species is similar to that which has been given to 

 lied Iron-Ore. We must except, however, the Brown 

 Iron-Froth which this division contains, since it properly 

 does not belong to the present species. Moreover, some 

 of what are generally considered as pseudomorphoses or 

 supposititious crystals, must be excluded, because they are 

 not real pseudomorphoses, consisting of compound varie- 

 ties of this species, but decomposed varieties of three 

 others, the hexahedral and prismatic Iron-pyrites, and the 

 brachytypous Parachrose-baryte, to which they must be 

 severally referred. The Fibrous Brown Iron-ore or Brown 

 Hematite contains the real crystals and the compound va- 

 rieties in stalactitic, reniform, and other imitative shapes, 

 also those massive varieties in which the composition still 

 may be ascertained. 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 the species 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 mass- 

 ^ es, the reniform one of alternating coats of different 

 colour and consistency, disposed in a reniform surface. 

 In the pisiform variety we meet with a similar composi- 

 tion, only in small globules, parallel to the surface of 

 which the lamellae are disposed. The compact pisiform 

 clay iron-ore, however, does not belong to the present 

 species, but it is decomposed prismatic Iron-pyrites, as is 

 demonstrated 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. 



