How to identify Iron Meteorite

To correctly identify Iron Meteorite (Iron-nickel alloy), 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

   Typically dark grey to black on the exterior (fusion crust), often with rust-colored patches due to terrestrial weathering. Freshly cut and polished surfaces are silvery-metallic.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Metallic on fresh surfaces; dull to sub-metallic on weathered surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Dense, compact. Etched surfaces reveal the characteristic Widmanstätten pattern (intergrowth of kamacite and taenite crystals). Some may show Neumann lines (shock-induced lamellae).

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Macroscopic crystal forms are not typically observed in hand samples. The internal structure is a crystalline intergrowth of kamacite (body-centered cubic) and taenite (face-centered cubic) iron-nickel alloys.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   No distinct cleavage. Exhibits hackly fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Not found in terrestrial geological environments. Occur as individual fall events on Earth's surface, often in arid regions (deserts) or polar ice fields where preservation and visibility are enhanced.

Key Facts

Hardness

4-5 on Mohs scale (for kamacite and taenite)

Specific Gravity

7.8-8.0 g/cm³ (significantly higher than most terrestrial rocks)

Crystal System

Kamacite: Isometric (body-centered cubic); Taenite: Isometric (face-centered cubic)

Color

Silvery-metallic on fresh surfaces; dark brown to black fusion crust on exterior, often with rust.

Luster

Metallic

Transparency

Opaque

Fracture

Hackly, irregular

Cleavage

None

Composition

Primarily iron (Fe) and nickel (Ni) alloy, with minor amounts of cobalt (Co), phosphorus (P), sulfur (S), and trace elements (e.g., Ga, Ge, Ir).

Physical characteristics

• Crystal Habit: Massive, anhedral intergrowths of kamacite and taenite, forming the Widmanstätten pattern upon etching.
• Cleavage Type: Absent
• Fracture Type: Hackly, irregular, tough
• Tenacity: Malleable to ductile (can be cut and shaped, though very hard)
• Luster Type: Metallic

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