Primary and Secondary Structures - Meteorites
New England Meteoritical Services
 
 

Recrystallized Kamacite
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Meteorite - Seneca Falls, IAB Iron.
 
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Figure 1. Scale bar 200 µm.

Meteorite - Seneca Falls
Classification - Iron, IAB-Mg, 8.2% Ni, 0.3 P
Recrystallized kamacite - Secondary.

Seneca Falls is a medium octahedrite with recrystallized primary structures (the kamacite was primary, but is now a secondary structure from recrystallization).

The meteorite experienced significant shock events, causing deformation and fracturing within its structure. Following the shock events, it was subjected to reheating.

This thermal metamorphism caused the recrystallization of the kamacite and taenite structures.

Specifically, kamacite was recrystallized to equiaxial grains 50 -250 µm in diameter. Berwerth (1914) examined the polyhedral kamacite grains and concluded that Seneca Falls had acquired its peculiar structure through artificial reheating.

Buchwald (1975) later reported that the shock-melted troilite and taenite lamellae are subdivided into segments, each 50 - 400 µm across, indicating severe shock-reheating. This led Buchwald to conclude that Seneca Falls's recrystallization is due to cosmic events.


 
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Figure 2. Scale bar 100 µm.
Recrystallized kamacite lamellae, Seneca Falls.
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Figure 3. Scale bar 300 µm.
Recrystallized kamacite lamellae, Seneca Falls.
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Figure 4. Scale bar 300 µm.
Recrystallized kamacite lamellae, Seneca Falls.
 
 
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