Stone yellow is a natural mineral material with high iron content, which has been formed for hundreds of millions of years and is called soil bone by miners. Its kernel is like egg yolk, and its shell is dark brown and hard as iron, also known as stone yellow.

The success rate of Shi Huang's works is less than 40%. Very picky about kiln firing temperature, too high or too low will lead to "total annihilation", but because of its high iron content, it is regarded as the first choice for health pots, so it reappears in the market.