I've never heard the expression, so I looked it up on Wiki
"A stone butch is a woman who is strongly masculine in character and dress, who tops her partners sexually (and sometimes emotionally), and who does not wish to be touched genitally. Not all stone butches identify in female terms, some are known to identify with male pronouns, and many stone butches do not identify themselves with lesbian or within the lesbian community. A common partner for a stone butch is a stone femme, who is a femme who bottoms sexually or who wishes not to touch the genitals of her stone butch partner. Butches are very diverse in emotion and sexual expression."