Which rock is used to make hampi ( Indian monument)?

The Jantar Mantar is a collection of architectural astronomical instruments. This instruments were built by Maharaja Jai Singh II at his then new capital of Jaipur between 1727 and 1734. These instruments can no longer make accurate observations because of the numerous tall buildings that have been built around the observatory.

The face of these masonry instruments is lined with marble and has astronomical gradations that may be used to give the local time according to the shadow cast by the triangle and to study the position of the sun and stars by using a metal rod.