Natural quasicrystal with decagonal symmetry

We report the first occurrence of a natural quasicrystal with decagonal symmetry. The quasicrystal, with composition Al₇₁Ni₂₄Fe₅, was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite. Icosahedrite, Al₆₃Cu₂₄Fe₁₃, the first natural quasicrystal to be identified, was found in the same meteorite. The new quasicrystal was found associated with steinhardtite (Al₃₈Ni₃₂Fe₃₀), Fe-poor steinhardtite (Al₅₀Ni₄₀Fe₁₀), Al-bearing trevorite (NiFe₂O₄) and Al-bearing taenite (FeNi). Laboratory studies of decagonal Al₇₁Ni₂₄Fe₅ have shown that it is stable over a narrow range of temperatures, 1120 K to 1200 K at standard pressure, providing support for our earlier conclusion that the Khatyrka meteorite reached heterogeneous high temperatures [1100 < T(K) ≤ 1500] and then rapidly cooled after being heated during an impact-induced shock that occurred in outer space 4.5 Gya. The occurrences of metallic Al alloyed with Cu, Ni, and Fe raises new questions regarding conditions that can be achieved in the early solar nebula.