Nature of Sedimentary Gem Deposits in Sri Lanka

The sedimentary gem deposits of Sri Lanka are known for producing a wide range of gemstone varieties. The most famous among these are the Ceylon sapphires, celebrated for their exceptional clarity, vibrant colours, and brilliance. In addition to sapphires, these deposits yield rubies, spinels, garnets, zircons, and many other gem species, making Sri Lanka a gemstone haven.

The gem-bearing gravels in these deposits are often found at varying depths, with some of the richest deposits being buried several meters below the surface. Traditional mining methods, such as pit mining and river panning, are commonly employed to extract these precious stones, with miners using simple tools and techniques that have been passed down through generations.

Sedimentary gem deposits in Sri Lanka are primarily formed through the process of weathering, erosion, and the subsequent transportation of mineral-rich materials by water. Over time, the weathering of parent rocks, particularly those rich in corundum (the mineral that forms sapphires and rubies), releases gem-quality crystals into the environment. These crystals are then transported by rivers and streams, eventually settling in low-lying areas where they accumulate to form alluvial deposits.