ANTIGORITE (Mg,Fe)3Si2O5(OH)4 (monoclinic)
kaolinite-serpentine group, varieties: baltimorite, bowenite, picrolite, williamsite, see also serpentine

variety baltimorite (a gray picrolite), also variety chrome-antigorite, purple to grayish white fibrous
Wood's Mine, Little Britain Township, Lancaster County, Pennsylvania