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Ilmenite
Current inventory:  1 gem
 

Chemistry:  Fe²⁺TiO₃  [Iron Titanium Oxide]

Discovered in 1827;   IMA status: Valid (pre-IMA; Grandfathered).
Ilmenite is named after the discovery locality; Ilmen Mountains, Chelyabinsk Oblast, Urals Region, Russia.

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/C.05-20

Nickel-Strunz 10th Ed. ID:

4.CB.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
C : Metal: Oxygen = 2: 3,3: 5, and similar
B : With medium-sized cations

Related to:

Ilmenite Group. Geikielite - Ilmenite Series. Ilmenite - Pyrophanite Series. The iron analogue of Geikielite, Pyrophanite and Ecandrewsite.

Crystal Data

Crystallography:

Trigonal - Rhombohedral

Crystal Habit:

Crystals are thick tabular crystals, with dominant base, to rhombohedral, to 25 cm. Skeletal, granular, massive; as lamellar exsolutions in hematite or magnetite.

Twinning:

Simple on [0001]; lamellar on [1011]

Physical Properties

Cleavage:

None

Fracture:

Conchoidal to Subconchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

4.68 - 4.76 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Weakly Magnetic

Optical Properties

Color:

Iron-Black, Black, Dark Gray with a brownish tint in reflected light

Transparency:

Opaque

Luster:

Metallic, Sub Metallic

Refractive Index:

2.40 - 2.42  Uniaxial ( - )  Anisotrophic

Birefringence:

0.00 Anisotrophic

Dispersion:

n/a

Pleochroism:

Weak; dark brown/pinkish brown

Anisotrophism:

Strong; color in reflected light: grayish white with brown tint; bireflectance: strong; O = pinkish brown, E = dark brown

Occurances

Geological Setting:

A common accessory mineral disseminated in igneous rocks, as granites, gabbros, and kimberlites; in granite pegmatites, carbonatites, and high-grade metamorphic rocks; may attain economic concentration in layered mafic intrusions and in “black sand” placer deposits.

Common Associations:

Apatite, Hematite, Magnetite, Pyrrhotite, Rutile, Ulvöspinel,

Common Impurities:

Mn,Mg,V

Type Locality:

Ilmen Mts, Chelyabinsk Oblast, Urals Region, Russia

Year Discovered:

1827

View mineral photos:

Ilmenite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Ilmenite is a common mineral, but rarely faceted. Ilmenite is a black, opaque mineral with high density, metallic luster and is Anisotropic. Faceted gems are attractive due to these attributes.
 

  
Ilmenite gems for sale: