1. Geological reasons: There are various geological environments under coal mines, such as stratum changes and coal seam structures, which will affect the flow of groundwater and lead to different mineral contents in groundwater. When the groundwater is rich in iron, the floor tile may appear red, which is formed by iron oxide on the surface of the tile. When the underground water is rich in minerals such as copper or copper-iron ore, the floor tile may appear green, which is formed by copper oxide on the surface of the tile.
2. Chemical reasons: In the process of coal mine production, various chemical reagents and drugs are often used, which may penetrate into the groundwater below the coal seam, thus affecting the color of floor tiles. For example, some chemicals used in coal mine production may make groundwater contain copper compounds, which may lead to green floor tiles.