How to identify Iron Ore

To correctly identify Iron Ore (Iron Ore), 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 is typically reddish-brown to steel-gray or black. Magnetite is black. Goethite and Limonite are yellowish-brown to dark brown. Siderite is typically yellowish-brown to grayish-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 and Limonite are earthy to dull. Siderite is vitreous to pearly.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be massive, granular, oolitic, pisolitic, banded (in BIFs), or earthy. Individual crystals may be fine-grained to coarse-grained.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hematite: Rhombohedral, tabular, botryoidal, massive, micaceous (specularite). Magnetite: Octahedral, granular, massive. Goethite: Acicular, fibrous, botryoidal, massive. Siderite: Rhombohedral, massive, granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Hematite: No true cleavage, but often exhibits parting. Magnetite: No cleavage. Goethite: Perfect in one direction (rarely observed). Siderite: Perfect rhombohedral cleavage in three directions.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Banded Iron Formations (BIFs) are found in ancient Precambrian shield areas. Magmatic deposits are associated with mafic/ultramafic igneous intrusions. Hydrothermal deposits occur in veins or replacement bodies in various rock types. Lateritic deposits are found in tropical weathering profiles. Bog iron ores are found in recent swampy environments.

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; Siderite: Trigonal.

Color

Variable: Reddish-brown, steel-gray, black, yellowish-brown, dark brown.

Luster

Metallic, submetallic, earthy, dull, vitreous, pearly.

Transparency

Opaque (most iron oxides), translucent (thin splinters of some goethite/limonite, siderite).

Fracture

Conchoidal to uneven (hematite, magnetite), uneven (goethite, limonite, siderite).

Cleavage

Hematite: No true cleavage, parting common; Magnetite: None; Goethite: Perfect in one direction (rarely observed); Siderite: Perfect rhombohedral.

Composition

Primarily iron oxides (Fe2O3, Fe3O4, FeO(OH)) or iron carbonate (FeCO3), often mixed with silica (SiO2) and other impurities.

Physical characteristics

• Crystal Habit: Massive, granular, botryoidal, oolitic, pisolitic, tabular, rhombohedral, octahedral, acicular, fibrous.
• Cleavage Type: Absent to perfect rhombohedral (depending on the specific mineral).
• Fracture Type: Conchoidal, uneven, splintery.
• Tenacity: Brittle.
• Luster Type: Metallic, submetallic, earthy, dull, vitreous, pearly.

Explore Iron Ore