1) Art material 2) Chinese invention 3) Hardstone carving 
An inkstone ({zh|t=硯|s=砚|p=yàn}) ({zh|t=硯臺|s=砚台|p=yàn tái}) (硯 suzuri) (벼루 byoru) is a stone mortar for the grinding and containment of ink. Other than stone, inkstones are also manufactured from clay, bronze, iron, and porcelain. The device evolved from a rubbing tool used for rubbing dyes dating around 6000 to 7000 years ago...
• (n.) A kind of stone containing native vitriol or subphate of iron, used in making ink.
Ink'stone' noun A kind of stone containing native vitriol or sulphate of iron, used in making ink.