Magnetite

Fe₃O₄

Non-silicate

Crystal system: cubic

Colour in hand specimen: black
Streak: black
Cleavage: none
Hardness: 7.5-8

Colour in plane polarised light: almost opaque
Relief: high
Isotropic

M501 Magnetite 
Brazil 
Crystals showing the characteristic octahedral form 
Silver-black colour 
Metallic lustre

M502 Magnetite 
Hay Tor, Devon 
A mass of small octahedral crystals embedded in a metamorphic rock 
Silver-black 
Metallic lustre 
No cleavage

L102 Hornblende biotite granite
L120 Granodiorite, accessory 
L141 Gabbro, olivine decomposition, accessory 
L162 Basalt, porphyritic, feldspar inclusion 
L172 Ultramafic cumulate, olivine alteration