Rock salt is the salt we usually eat. It is also called rock salt because it is produced in rocks. The chemical composition of stone salt is sodium chloride, and the crystal is cubic, large and transparent, so the ancients called it bright salt, crystal salt, yuhua salt and white salt. Rock salt is abundant all over the world. Zigong, Sichuan, China has always been known as the "Salt Capital", where there is stone salt about 40 meters thick. The thickness of salt layer in Yanyuan County, Panxi area, Sichuan Province is more than 1000 meters. Wanxian County, Huai 'an County, Jiangsu Province, Qianjiang County, Hubei Province and other places are known as the "gateway to eastern Sichuan" and are rich in stone salt reserves.

The wieliczka salt mine120m deep part has been mined, and the underground salt crystal palace and salt mine museum have been built. The surrounding rock walls are carved with three-dimensional animals and portraits, which are magnificent under the light, making people feel like they are in the "Crystal Palace". Every year, 700,000 tourists explore these wonders. There is also a special Yanjing hospital to let patients breathe salty air, which can treat asthma and lung disease, and the effect is the highest in children. More interestingly, the large crystalline rock salt there is also wrapped in marine plants and corals. This proves that this area used to be an ancient sea area.

Carl Salt Mine in Texas, USA is not only a mine for producing rock salt, but also used as an underground warehouse. This mine has been mined for nearly 60 years. 200 meters from the ground, on both sides of the abandoned tunnel, there are 15000 rooms, in which precious articles and documents are stored.

People all over the world eat about 35 million tons of salt every year. So, will the salt be consumed? I won't. Because in addition to rock salt, there are sea salt, pool salt, lake salt, well salt and so on. There are 2000 cubic kilometers of salt dissolved in the ocean. If it is used to build a wall with a width of 1 km and a height of 280 meters, it can circle the earth along the equator! There are 24 salt lakes in Qaidam Basin, Qinghai Province, China, with a salt reserve of more than 40 billion tons, which can be eaten all over the world 1000 years. The Qinghai-Tibet Highway is 32 kilometers long and crosses Chaerhan Salt Lake. It is paved with salt from subgrade to pavement. It is called "Zhang Wan Salt Bridge".