Duan inkstones are the most renowned in China. Its softness and ease of carving with a Mohs hardness of 3.5, is suitable for sculpting decorations. The highest quality is from the "Laokeng" quarry, which provides a smooth grinding experience and excellent water retention—ideal for oil soot ink.  This is why it is ideal for use with oil-based inksticks. The inkstone has a variety of stone patterns on the surface, and each pattern has its name.