It belongs to the so-called "pen, ink, paper and inkstone" in Four Treasures of the Study, and the contact between ink and inkstone is the most direct. However, today, unless it is a hobby or very particular, there are too many people who don't know about "inkstone".
Buy a box of ink, take whatever you want, dip your pen in some ink and you can start writing. However, in ancient times, the normal state of ink was not ink, but a huge object called "Mo Ding". Therefore, before using ink, there must be an inkstone and grinding ink.
Four Treasures of the Study is also an idiom, which can be explained as follows:
The old days were the floorboard of paper, ink, pen and inkstone. The inkstone, alias Mr. Mo, is the oldest treasure in Four Treasures of the Study. A study is a study. In the Northern Song Dynasty, Su Yijian wrote Four Books and Four Treasures of the Study, describing the types and authenticity of these four kinds of stationery. These stationery have a long history of production and a wide variety, with famous products and artists throughout the ages.
For example, Anhui Jingxian (formerly Ningguo House, whose paper was produced in the name of governing Xuancheng), Shexian (formerly Huizhou House) Huimo, Zhejiang (formerly Huzhou House) Hu Bi, Anhui Jingxian (formerly Ningguo House, whose pen was produced in the name of governing Xuancheng), and Guangdong Duanyan (formerly Zhaoqing House, formerly called Duanzhou).