Solution

• Placer deposits are formed by the concentration of a particular metal or mineral over a period of time. • The river while flowing through the rocks extract the minerals from there and they are deposited downstream under the influence of gravity. • These deposits are a result of depositions made by water, therefore placer deposits are found in or near subaqueous environments. • They are found in or near water bodies also in the sands of ancient river channels, dried valleys, beaches and coasts. • Generally, the inert metal like Gold and Platinum forms these kinds of deposits. • The reaction resistant ores like magnetite, monazite, zircon and rutile are also found in placer deposits. • The coastal plains of Alaska, India, NewZealand, Indonesia and South Africa are rich in placer deposits.