At least four allotropes of iron (differing atom arrangements in the solid) are known, conventionally denoted α, γ, δ, and ε.
The first three forms are observed at ordinary pressures. As molten iron cools past its freezing … 展开

Iron's abundance in rocky planets like Earth is due to its abundant production during the runaway fusion and explosion of type Ia supernovae, which scatters the iron into space.
Metallic or … 展开