A long time ago, people in the world were living a very hard life. At that time, people mainly relied on cutting down trees to make fire for cooking and heating. However, the growth rate of trees was far from meeting people's needs, and large areas of forests were gradually depleted. The reduction of forests led to a series of problems, such as raging sandstorms and floods, causing great distress to the people.
Seeing this situation, Tai Shang Lao Jun was deeply worried. He wanted to find a fuel that could meet people's living needs without excessive damage to the forests. Thus, Lao Jun began to continuously experiment and explore in his alchemy furnace. After countless attempts, he finally discovered a magical stone - coal.
Lao Jun decided to reveal the secret of coal to the world. One day, he sent two boys on cranes to appear in the dream of a local official. In the dream, the two boys said to him, "The immortal invites you, sir." Subsequently, the official got up and went on a crane. He saw white clouds floating around and stars shining. Soon, he arrived in front of a tall and majestic ancient-style building with the three seal characters "South Heavenly Gate" inscribed on the lintel. The official was puzzled as to why he had come to this place where immortals lived.
After entering the South Heavenly Gate, there was an even more magnificent pavilion. In the pavilion, the furnace fire was burning brightly. Two boys were fanning the fire, and an old man with flowing silver hair was holding a black stone and throwing it into the furnace. When the old man saw the official's arrival, he talked to him cordially. The official curiously asked, "Why is there no smoke from your furnace, and it burns so vigorously?" The two boys quickly replied, "This is Tai Shang Lao Jun. He is using the Bagua Furnace and burning the Sun Stone!" Lao Jun smiled and explained, "This is the essence of the earth refined by the Sun God - the Sun Stone, also known as the Onyx Gem or Magnetic Coal. Using it can save a large amount of wood."
The official remembered the fact that he had seen potters cutting down a large number of forests when inspecting people's conditions for many days. He was worrying about this matter. Hearing Lao Jun's words, he suddenly felt relieved, and his tiredness disappeared. So, he stepped forward and requested Lao Jun to bestow some treasures for the people's use. Lao Jun said, "There is a lot of this stone in the human world. Some are exposed on the surface, and some are buried deep underground. You can dig it up and use it by yourself. You can take some samples back." The official took the samples, thanked him, and left on a crane. Out of happiness, he suddenly woke up and realized that it was just a dream.
The official, following Lao Jun's instructions in the dream, led the potters to search for the Onyx Gem in the mountain valleys and gullies. After bringing it back to the kiln for trial burning, the fire was indeed burning vigorously. The heat was even higher than that of firewood, and there was no smoke. The ceramics fired were of solid quality, clear sound, and bright color. People were all full of praise. From then on, the burning gem bestowed by Lao Jun was called "coal." Because of this kind act of Lao Jun, people's lives were improved, and the forests were also protected. Therefore, Lao Jun was even more respected and loved by people.