A transparent, superfluid and super-dense state of matter, in between electron degenerate matter and quark degenerate matter. It is composed entirely of neutrons. Neutronium occurs naturally in neutron stars, where the gravitational pressure is sufficient to force such a state and is unstable at lesser pressures.
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Development Notes
Text by M. Alan Kazlev; additions by Adam Getchell
Initially published on 09 December 2001.

Significant revisions 23 February 2013.