Franklinite - Encyclopedia
Class : Oxides and hydroxides
Subclass : Oxides
Crystal system : Cubic
Chemistry : ZnFe2O4
Rarity : Rare to very rare
Franklinite belongs to the group of spinels with a normal structure. It is a rare mineral present in zinc-bearing metal deposits that have undergone contact metamorphism. It combines with zincite and willemite. It can also be found in certain slags. It owes its name to its location of discovery : the Franklin mine (New Jersey, USA) and also to honor the name of Benjamin Franklin, politician, physicist and inventor of the lightning rod who gave its name to the city. Franklinite occurs in granular or compact masses like magnetite, rarely in octahedral crystals with often rounded faces. Its luster is metallic, sometimes dull, its color brown-black to black. It is occasionally a zinc ore.
Main photo : 5 cm edged franklinite from Franklin Mine, Franklin, Sussex County, New Jersey, USA © Rock Currier
Franklinite in the World
Twinning
Twins are known on {111}.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 5.5 to 6
Density : 5.07 to 5.22
Fracture : Irregular to conchoidal
Streak : Red-brown to black
TP : Opaque
RI : 2.36
Birefringence : 0
Optical character : None
Pleochroism : None
Fluorescence : None
Solubility : Hydrochloric acid
Magnetism : None
Radioactivity : None