Decagonite
The second natural quasicrystal: an aluminium–nickel–iron alloy with tenfold symmetry.
Key facts
- Formula
- Al71Ni24Fe5
- Family
- Metals and alloys
- Crystal system
- Decagonal (a quasicrystal)
- First described
- the Khatyrka meteorite, 2015
Decagonite was described in 2015 from the Khatyrka meteorite. It is named after its tenfold symmetry. It was the second natural quasicrystal discovered.
What it is
Decagonite is a quasicrystal that is ordered in a repeating way along one direction but quasiperiodic, with tenfold symmetry, in the plane across it. It is like a stack of non-repeating tiled layers. Its composition matches a decagonal quasicrystal made in laboratories in the 1980s.
Where it is found
It was found as tiny grains in the Khatyrka CV3 chondrite, together with other aluminium alloys and silicates. Like icosahedrite, it is thought to have formed during a high-velocity collision in space.
How it is recognised
It is identified by electron and X-ray diffraction patterns that show tenfold symmetry.
Did you know?
A third natural quasicrystal, not yet named, was later found in the same meteorite.
Quasicrystals were later also found in fused rock from the first atomic bomb test, showing that they need extreme events to form in nature.