How to identify Magnetite

To correctly identify Magnetite (Magnetite), 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

   Black to brownish-black.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Metallic to submetallic.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically granular, massive, or as distinct octahedral or dodecahedral crystals. Can also be found as fine grains.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Cubic system, commonly forming octahedral crystals (eight-sided, double pyramids) or dodecahedral crystals (twelve-sided). Also occurs as granular masses.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, though it may exhibit parting on {111} planes.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Igneous rocks (e.g., gabbros, basalts, granites), metamorphic rocks (e.g., skarns, banded iron formations, amphibolites), and sedimentary rocks (e.g., placers, ironstones). Also found in hydrothermal veins.

Key Facts

Hardness

5.5-6.5 on the Mohs scale

Specific Gravity

5.17-5.18

Crystal System

Isometric (Cubic)

Color

Black to brownish-black

Luster

Metallic to submetallic

Transparency

Opaque

Fracture

Conchoidal to uneven

Cleavage

None, but parting on {111} is common

Composition

Iron oxide (Fe3O4)

Physical characteristics

• Crystal Habit: Octahedral, dodecahedral, granular, massive
• Cleavage Type: None, but parting on {111} planes due to twinning or exsolution lamellae
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Metallic to submetallic

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