freestone is a sandstone which can be worked freely in any direction.
"Geology"
James Geikie
When the building stone of which the houses are constructed is quarried, it is so soft that it can be easily moulded, or rather carved, into almost any desired shape, but exposure to the atmosphere hardens it gradually to the consistency of our American freestone.
"The Story of Malta"
Maturin M. Ballou
Any one who has noticed the action of frost upon brown freestone in our New England climate has a familiar example of what we describe.
"The Story of Malta"
Maturin M. Ballou