POTASH
Potash is a usable mineral resource resulting from accumulation of soluble potassium-bearing saline minerals in nature. It includes potassium-bearing brines and soluble solid potassium salts (e.g. sylvite, carnallite etc.) formed by evaporation, concentration and deposition of potassium-bearing water bodies.

In the world 95% of the potash is used for fertilizer. The main products are potassium chloride and potassium sulfate. It is one of the three major indispensable fertilizers. Only about 5% is used in industry. In industrial uses, 35% is used in the manufacture of detergents, 25% in the glass and pottery industry, 20% in the textile and dyeing industry, 13% in the manufacture of drugs, and the rest in the canned food, tanning, electric appliance and metallurgical industries. Potassium chlorate, superphosphate and nitrate are important ingredients in matches, fireworks, explosives and rockets.

Before the 1950s there was no potash industry in China and the soil fertility was maintained by farm manure. In the late 1950s China found the liquid potassium-magnesium salt mining area in the Qarhan Playa, Qinghai, and in 1963 China again found the Mengyejing solid potash mining area. Through a few decades of work, now an integrated mineral and fertilizer complex of liquid potassium-magnesium salt has been established in the Qarhan Playa and a potash production base has been formed there.

The soluble potash reserves demonstrated in China are not large and cannot meet the present enormous demands of agriculture for fertilizer. Therefore, potash is one of China's urgently needed mineral resources.

4.9.1 Resources

4.9.1.1 Reserves and Resources

Up to the end of 1997, China had explored 28 potash occurrences with retained reserves of 457 million tons (KCl), of which categories A+B+C reserves were 146 million tons (KCl). According to the Mineral Commodity Summaries 1997, the world's potash reserves were 8.4 billion tons (K2O) and the reserve base was 17 billion tons (K2O). The countries with the most abundant reserves are Canada, Russia and Byelorussia. The potash resource of China does not occupy an important position in China. China has considerable reserves of insoluble potassium-bearing minerals and rocks, e.g. alunite and K-feldspar, as well as potassium-bearing sandstone and shale. The retained reserves (category D and above category D) are 2,630 million tons (K2O) and the K2O content generally ranges from 9 to 12% with a maximum up to 35.74% (alunite deposits in Fujian). Although China has very abundant reserves of insoluble potassium-bearing minerals and rocks, as they are less soluble in water and the technology for the making of potassium fertilizer is complicated and costly, the development of these resources just starts now. It is expected that a new situation may appear in the near future.

4.9.1.2 Characteristics of Resources

(1) Geographical distribution

China's potash resources are rather deficient and distributed  very unevenly. The greater majority of the resources are distributed in  several modern saline lakes in the Qaidam basin of Qinghai Province and a small quantity in the vicinity of Jiangcheng, Yunnan (see Fig. 4.8.1).

(2) Characteristics of resources

    1) The potash-forming ages in China are mainly Quaternary, Cretaceous and Triassic. The representative deposits are clastic rock series type potash deposits and saline lake type potash deposits, e.g. the Mengyejing potash deposit in Yunnan and the Qarhan Playa in Qinghai.

    2) Liquid resources are dominant. The potash reserves abroad are mainly represented by those of ancient solid bedded potash deposits, which account for the greater majority of the total reserves; whereas potash reserves in China mainly come from liquid brine deposits.

    3) The ores are low-grade. The bedded solid potash beds in modern saline lakes consist commonly of lean ores, and 96% of the ores are out-of-balance ores with a KCl content of only 2 to 6%. The average KCl content of the ancient bedded potash deposits is 8.81%. The ore grade of bedded solid potash deposits abroad is generally 15 to 35% K2O.

   4) There are many associated components. Brines from salt lakes and underground brines also contain large amounts of magnesium, sodium, boron, lithium, bromine, iodine, rubidium and cesium besides potassium. They have very high value for total use.

    5) The potash salts are shallow-buried. Saline lake resources are exposed on the surface, and bedded solid potash salts are generally buried at depths of 25 to 700 m. They are easy to mine.

    6) The dressing possibility is poor. The potash salts in the Mengyejing potash deposit, Yunnan, contain appreciable quantities of insoluble substances in silty water and are low-grade. They are difficult to dress. Carnallite can only be concentrated by floatation after solar evaporation of the saline lake brines. This operation increases the investment of the salt field.