Mooihoekite is a copper iron sulfide mineral with the chemical formula of Cu9Fe9S16. It is a tetragonal-scalenohedral mineral containing copper, iron, and sulfur. The mineral was discovered in 1972 and received its name from its discovery area, the Mooihoek mine in Transvaal, South Africa.
- Category: Sulfide mineral
- Formula: Cu9Fe9S16
- Crystal system: Tetragonal
- Crystal class: Scalenohedral (42m)
- Color: Pale yellow. Tarnishes to pinkish-brown and purple.
Mooihoekite – a copper iron sulfide mineral
- Formula mass: 1,587.59 g/mol
- Crystal habit: Granular – Generally occurs as anhedral to subhedral crystals in matrix
- Mohs scale hardness: 4
- Luster: Metallic
- Streak: Black
- Diaphaneity: Opaque
- Specific gravity: 4.36
- Optical properties: Weakly anisotropic
It is found in massive sulfide from pipe-shaped dunite pegmatite in the norite zone of the Bushveld igneous complex in South Africa. It has also been found in troctolite from the basal Duluth gabbro in Minnesota, US; in the Talnakh area, Norilsk region, western Siberia; at Krzemianka, Poland; in the Malanjkhand copper-molybdenum deposit, Madhya Pradesh, India; and the Stillwater igneous complex in Montana, US.
Mooihoekite occurs in association with haycockite, magnetite, troilite, cuprian pentlandite, mackinawite, sphalerite, and moncheite in the Mooihoek mine and with haycockite, native copper, troilite, pentlandite, cubanite, and magnetite in the Duluth complex.
Mooihoekite is a rare mineral that is mostly used for research purposes. It has similar properties to chalcopyrite CuFeS2, making it helpful in the study of ore deposits and the study of the central portion of the Cu-Fe-S phase system.