How to identify Iron Ore

To correctly identify Iron Ore (Iron Oxide (e.g., Hematite, Goethite, Limonite)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Varies significantly: Hematite is typically reddish-brown to steel-gray/black; Magnetite is black; Goethite/Limonite are yellowish-brown to dark brown.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Hematite can be dull, earthy, or metallic (specular hematite). Magnetite is metallic to submetallic. Goethite/Limonite are typically dull, earthy, or silky.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be massive, earthy, oolitic, botryoidal, reniform, or micaceous (specular hematite). Banded Iron Formations exhibit distinct layering of iron-rich and silica-rich bands.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hematite: Rhombohedral, tabular, micaceous (specularite), botryoidal, reniform. Magnetite: Isometric, octahedral crystals. Goethite: Orthorhombic, acicular, fibrous, botryoidal, stalactitic. Limonite: Amorphous or cryptocrystalline aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Hematite: No true cleavage, but parting on {0001} and {1011}. Magnetite: No cleavage, but octahedral parting. Goethite/Limonite: No distinct cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Banded Iron Formations (BIFs) in Precambrian shield areas; lateritic deposits in tropical and subtropical regions; magmatic segregations in mafic and ultramafic intrusions; hydrothermal veins; sedimentary oolitic ironstones.

Key Facts

Hardness

Hematite: 5-6.5; Magnetite: 5.5-6.5; Goethite: 5-5.5; Limonite: 4-5.5 (Mohs scale)

Specific Gravity

Hematite: 5.26; Magnetite: 5.18; Goethite: 3.3-4.3; Limonite: 2.7-4.3

Crystal System

Hematite: Trigonal; Magnetite: Isometric; Goethite: Orthorhombic; Limonite: Amorphous/Cryptocrystalline

Color

Reddish-brown, steel-gray, black, yellowish-brown, dark brown

Luster

Metallic, submetallic, dull, earthy, silky

Transparency

Opaque

Fracture

Conchoidal to uneven

Cleavage

Hematite: No true cleavage, parting. Magnetite: No cleavage, parting. Goethite/Limonite: No distinct cleavage.

Composition

Iron oxides and hydroxides (Fe2O3, Fe3O4, FeO(OH))

Physical characteristics

• Crystal Habit: Massive, earthy, botryoidal, reniform, micaceous, oolitic, octahedral (magnetite), acicular (goethite)
• Cleavage Type: None to poor parting (hematite, magnetite)
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Metallic, submetallic, dull, earthy, silky

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