Saturday, 8 October 2016

Ceylon Sapphires

For centuries, the island of Sri Lanka has been a key source for a variety of gemstones, including sapphires. Sri Lankan gems were mined, set into jewelry, and traded abroad since at least 500 B.C. The Etruscans, Greeks, and Romans coveted sapphires, and the Indians called Sri Lanka “Ratna deepa,” which means “Island of Gems.”

Blue sapphires from Sri Lanka are known as Ceylon Sapphire. Ceylon Sapphires are unique in colour, clarity and lustre compared to the blue sapphires from anywhere else.
Marco Polo wrote that the island had the best sapphires, topazes, amethysts, and other gems in the world. Ptolemy, the 2nd century astronomer recorded that beryl and sapphire were the mainstay of Sri Lanka’s gem industry. Most consider Sri Lankan sapphires to be among the best in the world.

Colour gradation of blue ceylon sapphires, light to dark
Sapphires from Sri Lanka are known for their high clarity, rutile silk, and fingerprint inclusions. A range of colored sapphires can be found there, including rare padparadschas. Approximately 90 percent of the world’s star sapphires also come from the island.

Sapphire yields are estimated to be 60 percent blue, 25 percent yellow or orange, and 15 percent pink or purple.
Sri Lanka’s sapphires come from extensive gravel deposits located in the southern two-thirds of the island. Although the original source of this gravel remains unknown, scientists speculate that the parent rock is extremely old Precambrian metamorphic rock that makes up about 90 percent of the island.

Erosion of this parent rock created the extensive gem deposits along ancient and current riverbeds in the lower valleys.
Geologically speaking Sri Lanka is an extremely old country. Ninety percent of the rocks of the island are of Precambrian age, 560 million to 2,400 million years old. 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 the flood plains of rivers and streams. Metamorphic types of gems constitute 90% of the gem deposits in Sri Lanka.
Mining methods are relatively primitive and when gravel is extracted from current riverbeds, it is done with hand-made scrapers. On land, miners typically use picks, shovels, spades, and baskets. When shafts are sunk to reach the gravel, they are reinforced with palm and bamboo scaffolding and pumped to keep the water level down. At some locations, bulldozers scrape the overburden, but the gem gravel is washed by hand.