 The Khewra Salt Mine is also known as Mayo Salt Mine , in honour of Lord Mayo , who visited it as Viceroy of India . The mine is a part of a salt range that originated about 800 million years ago , when evaporation of a shallow sea followed by geological movement formed a salt range that stretched for about 300 kilometers ( 185 miles ) . The salt reserves at Khewra were discovered when Alexander the Great crossed the Jhelum and <unk> region during his Indian campaign . The mine was discovered , however , not by Alexander , nor by his allies , but by his army 's horses , when they were found licking the stones . <unk> horses of his army also recovered after licking the rock salt stones . During the Mughal era the salt was traded in various markets , as far away as Central Asia . On the downfall of the Mughal empire , the mine was taken over by Sikhs . Hari Singh <unk> , the Sikh Commander @-@ in @-@ Chief , shared the management of the Salt Range with Gulab Singh , the Raja of Jammu . The former controlled the <unk> mine , while the latter held Khewra . The salt quarried during Sikh rule was both eaten and used as a source of revenue . In 1872 , some time after they had taken over the Sikhs ' territory , the British developed the mine further . They found the mining to have been inefficient , with irregular and narrow tunnels and entrances that made the movement of labourers difficult and dangerous . The supply of water inside the mine was poor , and there was no storage facility for the mined salt . The only road to the mine was over difficult , rocky terrain . To address these problems the government levelled the road , built warehouses , provided a water supply , improved the entrances and tunnels , and introduced a better mechanism for excavation of salt . Penalties were introduced to control salt smuggling . While working with Geological Survey of India in the 1930s and 1940s , <unk> Sahni found evidence of angiosperms , gymnosperms and insects from the Cambrian period inside the mine . 
