Slate is also a sedimentary rock. The formation of the first slate of shale deposited in the soil bed, and later, the earth's movement so that they stacked layers of shale beds, the intensity of metamorphism to shale bed folded, shrink, and eventually slate. Slate component mainly silica. Its characteristics can be acid. According to Slate Slate component can be divided into three types:

(1) The plate carbonate stone: its composition silica content of less than 40% aluminum oxide content of less than 10% calcium oxide content of less than 15%, magnesium oxide content of less than 10%, ferric oxide content is 3% -7%.

(2) Clay Plate Stone: Its composition is mainly sericite, illite, chlorite, kaolinite and other clay minerals, which account for Slate for more than 80% of the mineral composition of its silica content of more than 50%, three oxidation 2 aluminum content greater than 12% calcium oxide content of less than 10%, magnesium oxide content of less than 5% of its iron oxide content is higher than the carbonate stone plate.

(3), carbonaceous, siliceous slate: from clay mineral composition between plate between the stone and carbonate stone plate, due to a stronger degree of silicification, silica content was high, very hard stone, the color darker.

Manifested in the structure of Slate flake or massive, fine particles, particle size in the 0.9-0.001mm are usually hidden between the crystal structure, more compact, and the most directional arrangement, rock cleavage are well developed in the thickness uniformity , moderate hardness, water absorption less. Its life is generally one hundred years.

Slate mostly monochrome color-based. Such as: gray, yellow, green, gray, green, cyan, black, brown red, red, purple and so on. As a single pure color, in the decoration, the tempting elegance and generous feeling. Slate generally is no longer polished, showing the natural shape, forming a natural beauty.

Therefore, the gravel and slate flower color of the text is superior to marble and granite, its decoration was also used in some places the rich cultural connotation