A lithophone is a musical instrument where the notes are made of stone.
With 'litho' referring to stone and 'phone' refereeing to sound.

Below is a public commissioned lithophone. 10 note lithophone tuned to an F major scale made from a single block of Kilkenny limestone (original weight of stone before I began carving the block was 1.7 tonne's). 

Below. 10 note marine themed limestone lithophone. With fish and crab relief carvings on either side.
This instrument is tuned to a major pentatonic scale with an added flat 3rd.