Page:Provincial geographies of India (Volume 4).djvu/90

74 The efflorescence known in India as "reh," which frequently covers the exposed surface of the Tertiary beds, is often found to contain a certain proportion of Carbonate of soda. This impure carbonate, contaminated with sand and mud, is known as "soap-sand" and is used for washing purposes by the Burmans.

Steatite or Soapstone is found in several places in the Arakan Yoma associated with serpentine; the best known mines are in the Minbu district.

The Burma Tin belt of Tenasserim and that of the Federated Malay States are continuous, and together constitute one of the world's greatest tin resources. The ore is the oxide, cassiterite, and is found in the neighbourhood of masses of intrusive granite. The greater part of the ore won comes from alluvial deposits of gravelly clay derived chiefly from the decomposition of the granite.

A fine dark emerald-green Tourmaline is mined to a small extent at Namôn in Karenni, and pink, brown or black types are obtained at Maingnin in Mongmit. The pink variety known as Rubellite is also obtained from the ruby mines.

Tungsten in the form of the oxide, Wolfram, has been mined in both Tavoy and Mergui during the past ten years or so, and is found also in Southern Shan States, Karenni, and Thatôn. Like tin it is closely connected with granite and is found in the many quartz veins which traverse this granite and the ancient sediments into which the latter has been intruded. The chief use to which tungsten is put is that of hardening steel. It differs from other hardening agents such as chromium, vanadium, etc., in that scarcely any diminution of hardness results from a rise in temperature. For this reason it is an invaluable constituent of the steel required for high-speed tools, which preserve their cutting capacity in spite of the high temperature caused by friction. The demand occasioned by the war greatly stimulated wolfram mining. In 1918—19, the out-turn amounted to 4443 tons.