The Mindat entry for Amianthus lists it as a synonym of brucite. This is incorrect.
Amianthus is either a serpentine or amphibole with fibrous structure (American Mineralogist, v. 63, pp.1023, 1978, see also Index Alphabetique de Nomenclature Mineralogique by Aballain, 1968).
I believe the Mindat entry was referring to Amianthöide Magnestite which was listed as Fe-rich brucite in Dana's Mineralogy 6th edition.