“I have never met a woman quite like you Anita,” Schnabel wrote. “You showed about life and myself and how to grow and become and exist with it all. The greatest woman I have ever known.”
Pallenberg’s other close friend, Bebe Buell — mother of actress Liv Tyler — paid her own tribute to the star.
“There was none more beautiful, more unique and more inspiring! The official “sixth Stone”… I will love you forever, dearest Anita.”
The actress, born in Italy in 1944, met The Rolling Stones backstage at one of their concerts in Munich, Germany. She began a romance with Brian Jones, but she left him after two years for Richards. She split from Richards in 1980.
Pallenberg and Richards shared a third child, a son named Tara, who died of Sudden Infant Death Syndrome in 1976.
This article originally appeared on PEOPLE