Widmanstätten Pattern

Definition

The Widmanstätten pattern is a distinctive crystalline structure observed in the cross-section of certain iron meteorites. It is characterized by a series of intersecting nickel-iron alloy bands or plates that form a unique and visually striking pattern.

5 Must Know Facts For Your Next Test

1. The Widmanstätten pattern is formed by the slow cooling of iron-nickel alloys in the interior of large iron meteorites over millions of years.
2. The pattern is a result of the phase transformation of the nickel-iron alloy from a high-temperature, disordered structure to a lower-temperature, ordered structure.
3. The width and spacing of the Widmanstätten bands are determined by the cooling rate of the meteorite, with faster cooling rates producing narrower bands.
4. The Widmanstätten pattern is a key diagnostic feature used to identify iron meteorites and distinguish them from other types of meteorites.
5. The presence and characteristics of the Widmanstätten pattern can provide information about the thermal history and formation conditions of the parent body of the iron meteorite.

Review Questions

• Explain the formation process of the Widmanstätten pattern in iron meteorites.
  • The Widmanstätten pattern is formed by the slow cooling of iron-nickel alloys within the interior of large iron meteorites over millions of years. As the meteorite cools, the nickel-iron alloy undergoes a phase transformation from a high-temperature, disordered structure to a lower-temperature, ordered structure. This phase transformation results in the formation of the distinctive intersecting bands of nickel-iron minerals, such as kamacite and taenite, that make up the Widmanstätten pattern.
• Describe how the characteristics of the Widmanstätten pattern can provide information about the thermal history and formation conditions of the parent body of an iron meteorite.
  • The width and spacing of the Widmanstätten bands are determined by the cooling rate of the meteorite. Faster cooling rates produce narrower bands, while slower cooling rates result in wider bands. By analyzing the specific characteristics of the Widmanstätten pattern observed in an iron meteorite, scientists can infer information about the thermal history and formation conditions of the parent body. This includes insights into the size, composition, and cooling rate of the parent body, which can help reconstruct the formation and evolution of the meteorite's source.
• Explain the significance of the Widmanstätten pattern in the identification and classification of iron meteorites.
  • The Widmanstätten pattern is a key diagnostic feature used to identify iron meteorites and distinguish them from other types of meteorites. The unique crystalline structure of the intersecting nickel-iron alloy bands is a distinctive characteristic of iron meteorites, and the specific features of the pattern can provide information about the meteorite's composition, thermal history, and origin. By analyzing the Widmanstätten pattern, scientists can classify iron meteorites into different groups and subtypes, which helps in understanding the diversity and evolution of these extraterrestrial materials.

Related terms

Nickel-Iron Alloy: A metallic alloy composed primarily of nickel and iron, which is a common constituent of iron meteorites.

Kamacite: A nickel-iron mineral that forms the lighter-colored bands in the Widmanstätten pattern.

Taenite: A nickel-iron mineral that forms the darker-colored bands in the Widmanstätten pattern.