Sri Lanka lies at the southern tip of India, at a latitude of 6° – 10° N and a longitude of 80° – 82° E. The central part of Sri Lanka comprises Precambrian crystalline rocks except for a belt of sedimentary rocks along the country’s northwest coast. The Precambrian rocks, which cover nearly 90% of Sri Lanka, have been classified into three central lithological units: Highland / Southwestern Complex, Vijayan Complex, and Wanni Complex.

Sri Lanka is well known worldwide for its large quantity and exquisite variety of gemstones. These gemstones occur mainly in alluvial gravels in valley bottoms that flow tributary hillside streams, which carry gem minerals released by weathering from the bedrock sources at hilltops or hillsides. Apart from the sedimentary formation, which carries gemstones, some rocks have been shown to contain gemstones, mainly varieties of Corundum. There are also gemstones associated with pegmatite, which constitute an essential source.

In early times, Sri Lanka was quite fittingly referred to as “Deepa,” which connotes “The Island of Gemstones.” The name Deepa is found in many chronicles. A Merchant’s Guide, “Periplus of the Erythrean Sea,” is presumed to have been compiled during the first century.

Today, around 200 minerals have been classified as gemstones due to their beauty, durability, rarity, or a combination of some attributes, which should be fulfilled to make a mineral worthy of being classified as a gemstone. Around 75 varieties of these gemstones have been mined or found in Sri Lanka. Although exploitation of Sri Lanka gemstone deposits has been going on for many centuries, it is only in recent times that effort has been made to study the industry itself, the locations of possible gemstone deposits, and most importantly.