The hardness of ft> stone shows that this kind of rock has high hardness and complete rock mass, and the hardness of most rocks exceeds 220 MPa, which is much higher than that of hard rock.

Hardness 1 degree: such as talc. Many Woods have equal hardness, and the hardness of rosewood can reach 2-3 degrees.

Hardness 2 degrees: such as gypsum. There are many frozen stones with the same hardness in Yin Zhangshi. The hardness of Tian Huangshi is about 2.5 degrees, and the hardness of human nails is 2-2.5 degrees.

Hardness 3 degrees: such as calcite. Individual varieties of Shoushan stone reach 3 degrees, and the hardness of copper keys is 3 degrees. The hardness of inkstones such as She Yan, Duanyan and Taoheshi is also around this hardness.

Hardness 4: raw materials for producing fluorite, also known as fluorite and hydrofluoric acid. The hardness of Russian material and Hetian jade is mostly 3.5-4 degrees.