SPECULAR OXIDE OF IRON. 
23 
SPECULAR OXIDE OF IRON. Cleaveland. 
Fer Oligiste. Hauy .—Rhombohedral Iron Ore. Jameson .—Specular Iron Ore. Thomson .—Specular Iron. Phillips, Dana 
and Shepard. —Oligiste. Beudant .—Rhomboedrisches Eisen-erz. Mohs. (It includes the true Specular Iron, Iron froth, 
Iron Mica, Red Hematite, Red Clay Ironstone, Red Siliceous Ironstone, Red Ochre, &c.) 
Under the above name are now included many varieties which pass into each other by 
almost imperceptible gradations, so that it is impossible to draw the line of specific distinction 
between them. 
Description. Colours dark steel-grey bordering on iron-black, iron-black and brownish red. 
The powder in all cases is some shade of red, usually cherry-red, or reddish brown. It is 
sometimes feebly magnetic. 
Occurs regularly crystallized ; in granular, lamellar and fibrous distinct concretions ; massive, 
disseminated, reniform, botryoidal, stalatitic and globular. 
The primary form is a rhombohedron. P on P' — 86° 10b 
P on P" = 93° 50b 
Fig. 6. 
The mineral sometimes assumes the form of an octa¬ 
hedron, sometimes of a triangular dodecahedron, with its 
apices truncated, either very deep, or near the apex. 
Lustre from splendent to dull, and is metallic or semi- 
metallic. Fracture conchoidal or earthy. Usually opaque, 
but sometimes thin laminae are faintly translucent. Hard¬ 
ness 5.5 to 6.5. Specific gravity 4.8 to 5.3 ( Jameson ); 
of a crystallized specimen from Sweden, 5.251 ( Hai - 
dinger). 
Infusible by the blowpipe per se, but melts with borax, 
and forms a green or yellow glass, like magnetic oxide of 
iron. It is soluble in hot muriatic acid. 
Distinctive characters. From the magnetic oxide of iron, which it often resembles, it 
may be distinguished by its red powder, and feeble action on the magnetic needle. 
Composition. The specular oxide of iron, when pure, is a peroxide of iron, containing in 
100 parts, 69.34 of iron, and 30.66 of oxygen. It seldom occurs in nature in this state of 
purity, but is generally mixed with silica, alumina, lime, &c.; and upon the proportion of 
these must depend the value of any particular variety of ore. In a table exhibiting the com¬ 
position of various specimens of the specular oxide, according to the analyses of Berthier 
and others, the amount of peroxide of iron varies from 28 to 99 per cent, the latter propor¬ 
tion being found only in a specimen from the department of Moselle, in France.* It may be 
Berthier. Traite des Essais par la Voie Seche, II. 223. 
