True about mounting stones is
The use of an articulator makes it necessary to mount the casts using a gypsum-producing product. These materials are referred to as "mounting" stones or plasters. They are fast setting and have low setting expansion. The mounting plaster has a sufficiently low strength to permit easy trimming and facilitate separating the cast from the articulator mounting plates.
Phillips Science of Dental Materials ed 12 pg 191
Fast setting
High expansion
High strength
All of the above