How to identify Iron Ore

To correctly identify Iron Ore (Iron Ore (likely containing hematite and/or goethite)), 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

   Highly variable, ranging from steel-gray to black (magnetite, specular hematite), reddish-brown to red (hematite), yellowish-brown to brown (goethite, limonite).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Metallic to submetallic (hematite, magnetite), dull to earthy (goethite, limonite).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be massive, granular, oolitic, banded, earthy, or micaceous (specular hematite).

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Individual minerals within iron ore can exhibit various crystal forms: hematite (rhombohedral, tabular, botryoidal, micaceous), magnetite (octahedral), goethite (acicular, botryoidal, stalactitic). However, in ore bodies, they are often massive or fine-grained 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 parting on {111}. Goethite: perfect cleavage on {010} but rarely observed in massive forms.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Banded Iron Formations (BIFs) are found in ancient Precambrian shield areas. Lateritic iron ores occur in tropical and subtropical regions with intense weathering. Oolitic ironstones are found in sedimentary basins. Magmatic deposits are associated with mafic/ultramafic igneous intrusions. Hydrothermal deposits are found in various tectonic settings.

Key Facts

Hardness

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

Specific Gravity

Hematite: 4.9-5.3; Magnetite: 5.18; Goethite: 3.3-4.3

Crystal System

Hematite: Trigonal; Magnetite: Isometric; Goethite: Orthorhombic

Color

As described above, highly variable depending on mineralogy.

Luster

As described above, metallic to earthy.

Transparency

Opaque

Fracture

Conchoidal to uneven (hematite, magnetite), uneven (goethite)

Cleavage

Hematite: no true cleavage, parting; Magnetite: no cleavage, parting; Goethite: perfect on {010} but rarely seen.

Composition

Primarily iron oxides (Fe2O3, Fe3O4, FeO(OH)) with varying amounts of gangue minerals (e.g., quartz, clay minerals, carbonates).

Physical characteristics

• Crystal Habit: Massive, granular, oolitic, banded, botryoidal, micaceous, earthy.
• Cleavage Type: None to poor (parting in hematite and magnetite, perfect in goethite but often obscured).
• Fracture Type: Conchoidal to uneven.
• Tenacity: Brittle.
• Luster Type: Metallic, submetallic, dull, earthy.

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