  The lack of benchmark data on the real minerals, native ammonium carriers in
Solar System gives rise to controversial opinions on extraterrestrial ammonium
reservoirs. We herein report on discovery of the first mineral carrier of
meteoritic ammonium and show its relevance to the compositional and spectral
characteristics of cometary and asteroidal bodies. Chemically distant from
previously inferred volatile organics or ammoniated phyllosilicates, it is an
aqueous metal-ammonium sulfate related to a family of so-called Tutton salts.
Nickeloan boussingaultite, (NH4)2(Mg,Ni)(SO4)2 6H2O, occurs in Orgueil, a
primitive carbonaceous chondrite closely related to (162173) Ryugu and (101955)
Bennu, the C-type asteroids. The available spectroscopic, chemical and
mineralogical data signify that natural Tutton salts perfectly fit into the
role of ammonium reservoir under conditions of cometary nuclei and carbonaceous
asteroids.
