Edward T. Rardman — On Mcematite in Tyrone. 397 



of this place, and it is not at all likely that the ancient miners 

 would venture to a depth sufficient to catch the 4 ft. 6 in. seam there. 



The above section is only approximately correct, as the junction 

 of some of the beds is not visible. The relative position of the 

 strata can, however, be distinctly traced, and the infcerstratification 

 of the ore-filled shales fully made out. They do not, like others of 

 the kind, lie in veins, pockets, or erosions in the limestone. In one 

 place, indeed, there is a slight depi'ession in the limestone under the 

 shale, but it is difficult to say whether it is due to erosion or to a 

 small fault. 



The nodules are raineralogically very peculiar. They are usually 

 in the form of a hollow shell, of, say, a quarter inch in thickness. 

 The greater part of this is made up of a very hard compact siliceous 

 brown hgematite, of a dai'k brown colour, but the interior is covered 

 with a thin coating of fibrous and mammillated limonite (Fig. 2 6). 

 When they are found in situ, and perfect, they often contain a kind 

 of nucleus of sandy shale or clay. (See Woodcut, p. 401.) 



The shale in which they occur is generally ochreous red, and seems 

 to be highly ferruginous. Being ajDparently very aluminous, as 

 well as in parts calcareous, it might be advantageously used as a 

 flux for the ore were it worked. In this way the whole bed might 

 perhaps be utilized. 



That the ore is of excellent quality for the smelter will be perceived 

 from the following analysis. The specimens used were taken at 

 random from a large heap left after the new workings were dis- 

 continued, and were not the very best,* for those had been taken 

 away before, and Dr. Eitchie, of Belfast, informed me that some he 

 had estimated yielded over 60 per cent, of iron. 



Analysis of Ore. 



FejOj 74-56 HoO (Hygroscopic) 2-90 



FeO a trace MnO, a trace 



MgO 0-044 CO2 ' a trace 



CaO a trace PoOg a trace 



SiCetc 9-42t ' 



AI363 3-51 100-674 



HaO (combined) 10-24 Metallic Iron = 52-20 



This seems to give the composition of Gothite, Fe2H204, | — a 

 ■ metahydrate which is a usual form of brown haematite, — together with 

 a hydrous silicate of alumina, such as Kaolin, and some free silica. 

 It might be nearly represented by the formula — ■ 



14Fe3H204 + Al2Si2072H30 + 2Si03. 

 Gothite. Kaoliii or Clay. Silica. 



There was a total absence of sulphur, and the merest trace of 

 phosphoric acid could only be detected by the most delicate test : 

 thus the ore is extremely well suited for the manufacture of Bessemer 

 steel. For a brown haematite the per-centage of iron is very high ; 

 and from its composition it seems to be well adapted for admixture 



* I found even better specimens, in appearance, in the thin shale-beds. 



t Soluble silica, together with the insohible residue, containing a little alumina. 



X Manual of Geology (Jukes and Gcikie), p. 63. 



