1. Longer exposure: Mignonite will cause its color to fade when exposed to sunlight and air for a long period of time.
2. Repeated floating in the water: Mokume gane, if placed in the water for a long time, or repeatedly dipped and floated, can also lead to the fading of its color.
3. Prolonged exposure to strong acid or alkali: the color of mokume gane will be affected by chemical reaction when it is exposed to strong acid or alkali for a long time.
4. Degree of wear and tear: If the mullet stone has ever been repeatedly worn or scratched, or contacted with hard objects, it will also cause its color to fade or disappear.