Rosenbergite is a mineral with the chemical formula AlF₃·3H₂O. It is a trihydrate of aluminium fluoride.

Rosenbergite
Acicular rosenbergite crystals from Le Cetine Mine, Siena, Tuscany, Italy
General
Category	Mineral
Formula (repeating unit)	AlF3·3H2O
IMA symbol	Ros[1]
Crystal system	Tetragonal
Crystal class	4
Space group	P4/n (no. 85)
Identification
Mohs scale hardness	3–3.5

It is colorless. Its crystals are tetragonal to dipyramidal. It is named after Philip E. Rosenberg, a United States geochemist. It is found in the Celtine Mine in Tuscany, Italy and Mount Erebus, Ross Island, Antarctica. It is not radioactive. Rosenbergite is rated 3–3.5 on the Mohs Scale.