free·stone 
(frēstōn′)
(frēstōn′)n.
1. A stone, such as limestone, that is soft enough to be cut easily without shattering or splitting.
2. A fruit, especially a peach, that has a stone that does not adhere to the flesh.
[Middle English freston, translation of Old French franche pere, high-grade stone : franche, high-grade, feminine of franc, noble, freeborn + pere, stone.]
freestone′ adj.