Solution

Limestone often contains magnesium carbonate, either as dolomite CaMg (CO3) 2 or magnesite (MgCO3) mixed with calcite. Such rocks are termed as 'dolomitic' or 'magnesian' limestone. Limestone altered by dynamic or contact metamorphism becomes coarsely crystalline and is referred to as 'marble' and 'crystalline limestone'. Although the largest reserves are located in Andhra Pradesh, Rajasthan was the leading producing State accounting for (20%) of the total production of limestone, followed by Madhya Pradesh & Andhra Pradesh (13% each). A placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. Gold is often liberated from the Rocks by weathering and its particles get concentrated at certain places in the rivers. Such deposits are then recovered by a process called panning. These placer deposits, also called Alluvial gold are obtained from the Sands of the Subarnarekha River and the Sona Nadi in the Singhbhum District of Jharkhand.