Rock Salt Mines

The Khewra Salt Mine (or Mayo Salt Mine) is located in Khewra, north of Pind Dadan Khan, an administrative subdivision of Jhelum District, Punjab Region, Pakistan, which rises from the Indo-Gangetic Plain. It is Pakistan's largest, the world's 2nd largest  and the oldest salt mine in the world. It is a major tourist attraction, drawing up to 250,000 visitors a year. Its history dates back to its discovery by Alexander's troops in 320 BC, but it started trading in the Mughal era. The main tunnel at ground level was developed by Dr. H. Warth, a mining engineer, in 1872 during British rule. After independence, the Pakistan Mineral Development Corporation took over the mine, which still remains the largest source of salt in the country, producing more than 350,000 tons per annum of about 99% pure halite. Estimates of the reserves of salt in the mine vary from 82 million tons to 600 million tons.

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 Mianwali 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. Ailing 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 Nalwa, the Sikh Commander-in-Chief, shared the management of the Salt Range with Gulab Singh, the Raja of Jammu. The former controlled the Warcha 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, Birbal Sahni found evidence of angiosperms, gymnosperms and insects inside the mine which he regarded as originating from the Eocene period, but which Michael Cremo alleged originated from the Cambrian period. However, Cremo's opinion is not supported by contemporary geologists.

Khewra Salt Mine is situated in Pind Dadan Khan Tehsil of Jhelum District. Located about 160 km (100 miles) from Islamabad and Lahore, it is accessed via the M2 motorway, about 30 kilometers (20 miles) off the Lilla interchange while going towards Pind Dadan Khan on the Lilla road. The mine is in mountains that are part of a salt range, a mineral-rich mountain system extending about 200 km from the Jhelum river south of Pothohar Plateau to where the Jhelum river joins the Indus river.Khewra mine is about 288 meters (945 feet) above sea level and about 730 meters (2400 feet) into the mountain from the mine entrance. The underground mine covers an area of 110 km² (43 sq. miles)

Estimates of the total reserves of salt in the mines range from 82 million tons to 600 million tons. In raw form it contains negligible amounts of Calcium, Magnesium, Potassium, Sulphates and moisture, with Iron, Zinc, Copper, Manganese, Chromium and Lead as trace elements. Salt from Khewra, also known as Himalayan salt, is red, pink, off-white or transparent. In the early years of British rule, the Khewra mine produced about 28,000 to 30,000 tons per annum; it increased to about 187,400 tons per annum for the five fiscal years ending 1946–7 and to 136,824 tons for the two years ending 1949–50 with the systematic working introduced by Dr H. Warth. The mine's output was reported in 2003 to be 385,000 tons of salt per annum, which amounts to almost half of Pakistan's total production of rock salt. At that rate of output, the tunnel would be expected to last for another 350 years.