Images
Formula: CuFe2S3
Sulphide, isometric paramorph of orthorhombic
cubanite
Crystal System: Isometric
Specific gravity: 4.075 calculated
Hardness: 3½
Colour: Bronze, yellow, brown
Common impurities: Zn
Environments
Volcanic igneous environments
Hydrothermal environments
Isocubanite occurs as a primary sulphide precipitate
from hot, saline solutions that cool under seawater (black smokers), in hydrothermal
copper sulphide deposits, and in pumice from
volcanic eruptions (HOM, Dana, Webmin). Associated minerals include
chalcopyrite,
pyrrhotite, pyrite,
sphalerite, wurtzite and
anhydrite
(HOM).
Isocubanite can be formed from cubanite by heating to between
200oC and 270oC; it is stable above 250oC
(Dana).
Localities
The type locality is EPR 21° N, Juan de Fuca Ridge complex, East Pacific Rise, Pacific Ocean.
Alteration
Cubanite is very sensitive to temperature, pressure and compositional variations. In the laboratory
cubanite has been transformed to isocubanite by increased pressure at ~4 GPa at room
temperature. These results could be useful in estimating the metamorphic pressure conditions of
cubanite-bearing carbonaceous chondrites
(CM 48.1137-1147).
A sample of isocubanite from the Mid-Atlantic Ridge at 23oN transformed after a few months to a mixture of similar amounts of
chalcopyrite and a phase of composition close to CuFe3S4
(AM 80.186).
Back to Minerals