Q. Storehouse of minerals?

in addition to the earth's crust, oceans also provide a huge storehouse of minerals in which the metals occur primarily as soluble sulphates and halides. It is estimated that one cubic kilometre of sea water contains 1 million tonnes of magnesium, 1,500 tonnes of strontium and 5 tonnes each of gold, copper, manganese, zinc and lead. Magnesium is already being extracted from sea water. In future, greater attention will be paid to sea as a source of raw materials when supplies of ore deposits on land are depleted. In addition to sea water, nodules or lumps about the size of an orange have been found on sea bed at depths of 4,000-5,000 metres. The nodules are relatively rich in manganese (25%) and iron (15%). Recently technology for deep sea mining of these nodules has been developed.