Images
Formula: Fe2+Ti4+O3
Simple oxide, ilmenite group,
titanium-bearing mineral
Varieties
Picroilmenite is a magnesium-rich variety of ilmenite
Crystal System: Trigonal
Specific gravity: 4.68 to 4.76 measured, 4.789 calculated
Hardness: 5 to 6
Streak: Black to reddish brown
Colour: Black
Solubility: Slightly soluble in hydrochloric acid
Common impurities: Mn,Mg,V
Environments:
Igneous environments
Placers
Metamorphic environments
Ilmenite is a high-temperature primary mineral that is
a common accessory in igneous and metamorphic rocks. It is often concentrated in placers as "black
sand" deposits
(Webmin).
It may be found in
anorthosite (R&M 93.2.146),
basalt,
gabbro,
kimberlite and
syenite.
As a constituent of black sands it is associated with
magnetite,
rutile,
zircon and
monazite.
It is a mineral of the granulite facies.
Localities
At the Faraday mine, Faraday Township, Hastings county, Ontario, Canada, ilmenite to 30 kg occurs with
magnetite of similar size
(R&M 94.5.413) .
Amity, Town of Warwick, Orange county, New York, USA, is an area of
granite intrusions into
marble and associated
gneiss. The marble is
mostly composed of white crystalline calcite that often has small flakes
or spheres of graphite and
phlogopite. Ilmenite occurs as black metallic crystals to 3 cm
associated with
spinel, chondrodite and
phlogopite in marble.
(R&M 96.5.437).
Alteration
Ilmenite may alter to hematite or
rutile
(AJM 18.2.26).
aenigmatite, anorthite
and O2 to hedenbergite,
albite, ilmenite and magnetite
½Na4[Fe2+10Ti2]O4[Si12O36] +
CaAl2Si2O8 + ½O2 = CaFe2+Si2O6 +
2NaAlSi3O8 + Fe2+Ti4+O3 +
Fe2+Fe3+2O4
(DHZ 2A p651)
amphibole, chlorite,
paragonite, ilmenite, quartz
and calcite to garnet,
omphacite, rutile, H2O
and CO2
NaCa2(Fe2Mg3)(AlSi7)O22(OH)2 +
Mg5Al(AlSi3O10)(OH)8 +
3NaAl2(Si3Al)O10(OH)2 + 4Fe2+Ti4+O3 +
9SiO2 + 4CaCO3 →
2(CaMg2Fe3)Al4(SiO4)6 +
4NaCaMgAl(Si2O6)2 + 4TiO2 + 8H2O +
4CO2
In low-grade rocks relatively rich in calcite the
garnet-omphacite association may be
due to reactions such as the above
(DHZ 2A p453).
amphibole, clinozoisite,
chlorite, albite, ilmenite and
quartz to garnet,
omphacite, rutile and H2O
NaCa2(Fe2Mg3)(AlSi7)O22(OH)2 +
2Ca2Al3[Si2o7][SiO4]O(OH) +
Mg5Al(AlSi3O10)(OH)8 + 3NaAlSi3O8 +
4Fe2+Ti4+O3 + 3SiO2 →
2(CaMg2Fe3)Al4(SiO4)6 +
4NaCaMgAl(Si2O6)2 + 4TiO2 + 6H2O
In low-grade rocks relatively poor in calcite the
garnet-omphacite association may be
developed by the above reaction
(DHZ 2A p453).
augite, albite,
pyroxene, anorthite and
ilmenite to
omphacite, garnet,
quartz and rutile
2MgFe2+Si2O6 + Na(AlSi3O8) +
Ca2Mg2Fe2+Fe3+AlSi5O18 +
2Ca(Al2Si2O8) + 2Fe2+Ti4+O3 →
NaCa2MgFe2+Al(Si2O6)3 +
(Ca2Mg3Fe2+4)(Fe3+Al5)(SiO4)9
+ SiO2 + 2TiO2
This reaction occurs at high temperature and pressure
(DHZ 2A p449).
titanomagnetite (ilmenite combined with magnetite),
quartz, and
aegirine-hedenbergite to
aenigmatite, hedenbergite,
magnetite and O2
6(Fe2+Ti4+O3 + Fe2+Fe3+2O4) +
12SiO2 + 12(NaFe3+Si2O6 + CaFe2+Si2O6)
⇌
3Na4[Fe2+10Ti2]O4[Si12O36] +
12CaFe2+Si2O6 + 2Fe2+Fe3+2O4 +
5O2
(DHZ p652)
Back to Minerals