"Become stone" is a figurative expression used to describe a state of emotional or mental hardness or insensitivity. However, there are many other words that can be used as synonyms to communicate the same meaning. For instance, the phrases "petrify", "harden", "numb", "stiffen", "solidify", and "frigidify" are all examples of alternative expressions that can be used in place of "become stone". Each of these phrases has a slightly different connotation, so it's important to choose the appropriate phrasing for the specific context. Regardless of the specific wording chosen, however, all of these expressions speak to emotional detachment and a lack of empathy.