There are both natural and man-made. Natural called west red, is basically pure iron oxide, red powder. Due to the different production methods and operating conditions, their crystal structure and physical properties are very different, and the color varies from orange to blue to violet. Both hiding power and tinting power are great. Density 5-5.25. It has excellent light resistance, high temperature resistance, and resistance to atmospheric effects, dirt gas resistance, all alkali resistance. Only when heated in concentrated acid will it gradually dissolve.