ABSTRACT
The Mirovo salt deposit is located approximately 5 km south-east of the town of Provadija, in the Varna province, Bulgaria. That is a unique natural phenomenon with its origin, composition, location and geophysical characteristics. The Mirovo salt diapir has a depth of approximately 4000 m and its top (the “salt mirror”) is 15 to 20 m deep. The diapir has a base area of the order of 200 km2 and generally has the shape of a truncated cone. Approximately 73% of the diapir is sodium Chlorid, the remainders comprising insoluble elements and other evaporites, irregularly distributed through the salt mass. It was excavated in 1919. A factory was constructed and the production of common salt began in 1924. However, the industrial exploitation of the salt pit began in 1954 after the construction of the first soda plant in the Devnya lowland. The method of boring is applied at present in the salt pits (more than 30 utilized boreholes) and more specifically the method of underground salt leaching through which one major raw material for the Devnya chemical plants is produced — brine.
