464 PROFESSOR HEDDLE ON 
It yielded, on 1° 304 grammes— 
Ferric Oxide, . : : ; : 78° 787 
Ferrous Oxide, . ; : ee 3206 
Manganous Oxide, . : : . *153 
Alumina, . , 4 { : : “956 
Lime, . 4 j : . , . *472 
Silica, : E ; ’ ; f 3° 067 
Water, ; j ‘ : d : 14:314 
100: 589 
When dissolved in cold HCl, a small quantity of light flocculent silica 
separates ; upon applying heat, this goes entirely into solution. 
2. The second variety of limonite at this locality I found directly coating the 
sandstone in one or two specimens. But it in general has assumed the botryoidal 
forms of the psilomelane; occasionally it is somewhat stalacitic, especially 
when it directly coats sandstone. 
The surface of the mineral is highly polished, jet black, and splendidly 
lustrous. Its internal structure is divergent-fibrous; but it is tough. The 
internal colour is purplish-brown, and the lustre satin-like, or almost vitreous. 
Its powder is a very rich ochre-yellow. 
It yielded— 
Ferric Oxide, t § E 3 : 82-135 
Manganous Oxide, : i i : - 343 
Lime, . : 4 : : : : aye 
Magnesia, . ; : ; ; : *214 
Silica, ; F é : ; , 8 ok 
Water, , ; : : : , 1S OT 
100 : 468 
Here, also, some of the silica was in combination. The thickness of the 
coatings of this variety of limonite varies from the fourth of an inch to films of 
extreme thinness ; these can always be discriminated from the psilomelane, by 
their brilliant lustre, and of course by their ochre tint. This variety, for the 
most part, forms the black hematite of old authors. 
The results of these two analyses of limonite, taken in conjunction with the 
analyses of the psilomelane and of the wad, with which the limonite is associated, 
showa most peculiar antagonism to exist between the two closely chemically-allied 
metals, iron and manganese. Though here occurring together, formed to some 
extent possibly by similar processes, and superimposed in layers over each 
other, the iron ore has almost absolutely repelled the manganese; while no 
specimen of the psilomelane which I have examined contained a trace of iron. 
