How to identify Iron Ore

To correctly identify Iron Ore (Iron oxides (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 widely depending on the dominant iron mineral: Hematite (red, reddish-brown, steel-gray, black), Magnetite (black), Goethite/Limonite (yellowish-brown, dark brown, black), Siderite (yellowish-brown, gray, white).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Hematite (metallic to dull/earthy), Magnetite (metallic to submetallic), Goethite/Limonite (silky, dull, earthy), Siderite (vitreous to pearly).

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

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

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hematite: Rhombohedral, tabular, botryoidal, reniform, massive. Magnetite: Octahedral, dodecahedral, massive, granular. Goethite: Prismatic, acicular, botryoidal, stalactitic, massive. Limonite: Amorphous, earthy, massive. Siderite: Rhombohedral, tabular, massive, granular.

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 on {010}. Limonite: None. Siderite: Perfect rhombohedral on {1011}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Banded Iron Formations (BIFs) in ancient cratons, lateritic weathering profiles in tropical and subtropical regions, hydrothermal veins, magmatic intrusions (e.g., Kiruna-type deposits), and sedimentary bog iron deposits.

Key Facts

Hardness

Hematite: 5-6.5; Magnetite: 5.5-6.5; Goethite: 5-5.5; Limonite: 4-5.5; Siderite: 3.5-4.5 (Mohs scale)

Specific Gravity

Hematite: 4.9-5.3; Magnetite: 5.18; Goethite: 3.3-4.3; Limonite: 2.7-4.3; Siderite: 3.96

Crystal System

Hematite: Trigonal; Magnetite: Isometric; Goethite: Orthorhombic; Limonite: Amorphous; Siderite: Trigonal

Color

Variable (red, black, brown, gray, yellow)

Luster

Metallic, submetallic, dull, earthy, silky, vitreous

Transparency

Opaque (most iron oxides), translucent (thin splinters of goethite, siderite)

Fracture

Conchoidal, uneven, splintery, earthy

Cleavage

Hematite: None (parting); Magnetite: None (parting); Goethite: Perfect on {010}; Limonite: None; Siderite: Perfect rhombohedral

Composition

Iron oxides (Fe2O3, Fe3O4), iron oxyhydroxides (FeO(OH)), iron carbonates (FeCO3)

Physical characteristics

• Crystal Habit: Massive, granular, botryoidal, reniform, tabular, octahedral, rhombohedral, earthy
• Cleavage Type: None to perfect rhombohedral (siderite), perfect prismatic (goethite)
• Fracture Type: Conchoidal, uneven, splintery, earthy
• Tenacity: Brittle
• Luster Type: Metallic, submetallic, dull, earthy, silky, vitreous

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