366 On Metallic Minerals. 



MINERALOGICAL CHARACTERS.* 

 SPECULAR OXIDE OF IRON 



Colour on a fresh fracture lavender blue, externally rusty 



red opaque structure compact granular- — fracture 



uneven — lustre glistening metallic — yields to the knife but 

 strikes fire under the hammer — colour of pmvder dark 

 broivnish red — shape of fragments prismatic — specific gra- 

 vity 4-9 slightly magnetic — not soluble in ivarm muriatic 

 acid — infusible alone before the blow-pipe, but with borax 

 forms a bead coloured by iron. 



The characters in Italics have induced me to name 

 this the specular oxide of iron, although it certainly 

 possesses nothing of that brilliancy of lustre and pavonine 

 tarnish so frequently characterestic of that ore. 



It is found enveloped by the other ores and is the only 

 oneof metallic lustre among them. It should yeild 63 or 

 64 per cent, by calculation. 



SPARRY IRON ORE AND RED OCHRE. 



Colour dark red (Indian red,) with yellow laminar parts 

 interspersed, sometimes these parts form a yellow band in 

 the middle of the mass, which on a cross fracture by a 

 strong contrast between the real and the yellow produces a 

 pleasing effect — opaque — structure between earthy and 

 laminar, the mass having the appearance of being com- 

 posed of red ochre and sparry iron. The laminar parts 

 have about the hardness of fluor, but the earthy portion 



• It is perhaps necessary to say tbat in giving these characters or others 

 which may follow, I have been uninfluenced by a communication in the Irt 

 vol. of the Society's Transactions, iu which the characters of a /Ci/; of the 

 Marmora ores appear. Having the advantage of the writer of that article, 

 which a vi^it to the spot has atiorded, my observations both on its rocks and 

 minerals, erroneous or not, are at least unbiassed either by that communi- 

 cation or by any other. 



