Sri Lanka's gem industry has a very long and colorful history. Sri Lanka was affectionately known as Ratna – Dweepa which means Gem Island. The name is a reflection of its natural wealth. Marco Polo wrote that the island had the best sapphires, topazes, amethysts, and other gems in the world. Ptolemy, the second century astronomer recorded that beryl and sapphire were the mainstay of Sri Lanka's gem industry. Records from sailors that visited the island states that they brought back "jewels of Serendib". Serendib was the ancient name given to the island by middle – eastern and Persian traders that crossed the Indian Ocean to trade gems from Sri Lanka to the East during the fourth and fifth century.
Sri Lanka, geologically speaking is an extremely old country. Ninety percent of the rocks of the island are of Precambrian age, 560 million to 2,400 million years ago. The gems form in sedimentary residual gem deposits, eluvial deposits, metamorphic deposits, skarn and calcium-rich rocks. Other gems are of magmatic origin.
Residual deposits are mainly found in flood plains of rivers and streams. The metamorphic types of gems constitute 90% of the gem deposits in Sri Lanka. Sri Lanka has the highest density of gem deposits compared to its landmass. Ratnapura contains the most gem deposits and derived its name from the gem industry. Ratnapura means "city of gems". .
The blue sapphires from Sri Lanka are known as Ceylon Sapphire. Ceylon Sapphires are reportedly unique in colour, clarity and lustre compared to the blue sapphires from other countries.