Sri Lanka, the island nation off the southern tip of India, is one of the oldest and richest gem sources in the world. Its gem gravels, especially around Ratnapura, yield blue sapphire, the pink-orange padparadscha, cat's eye chrysoberyl, moonstone, spinel, garnet, zircon and many other species, often all from the same pit. Traders from the ancient Mediterranean, Arabia and China knew the island for its gems, and much of the mining is still done by hand in shallow pits.
Geology of the gem gravels
Most of Sri Lanka is built on very old metamorphic rock, part of a belt of high-grade gneisses and related rocks. Gems formed in these rocks and in pegmatites and other bodies within them under high heat and pressure. Over long periods, weathering broke down the host rock in the island's hot, wet climate, and rivers carried the hard, heavy gem crystals downstream.
The gems collected in layers of gravel buried under clay and sand in valleys and old river channels. Local miners call this gem-bearing gravel "illam." Because many different minerals weathered out of the same rocks, a single illam layer can hold a wide mix of species. The process is explained on the sedimentary rock cycle and metamorphic rocks pages.
Ratnapura, the City of Gems
Ratnapura, in the Sabaragamuwa province of southwestern Sri Lanka, is the island's best-known gem center. Its name is usually translated as "city of gems." The surrounding valleys and hills hold extensive illam layers, and gem mining, trading and cutting are major parts of local life. Other gem areas include Elahera in the central part of the island and districts in the south and east.
Ratnapura has a busy gem market where brokers and dealers trade rough and cut stones. Buyers from many countries come to the town, and Sri Lanka has its own gem authority that oversees mining licenses and exports.
Illam pit mining
Traditional Sri Lankan gem mining is small-scale and mostly manual. Miners dig a square pit down through clay and soil to reach the illam, shoring the walls with timber and ferns. Depth varies with the site, from a few meters to much deeper. Water is a constant problem and is pumped out, historically by hand and now often with small engines.
Miners haul the gravel to the surface in baskets. It is then washed in round, shallow wicker baskets, swirled in water so that light material spills out and heavy gems settle to the bottom. A skilled washer picks out the gem crystals by eye. Some mining also takes place in riverbeds. Sri Lanka has long restricted large mechanized mining in many areas, and much of the country's production still comes from these small pits.
Blue sapphire
Sri Lanka, long known in the trade as Ceylon, is one of the classic sources of sapphire. Ceylon sapphires are known for a bright, lively blue, often lighter and less saturated than some other sources, which shows well in many lighting conditions. The island also produces yellow, pink, violet, white and color-change sapphire.
Much Sri Lankan material comes out of the ground as pale or milky "geuda" sapphire. In the late 20th century, Thai and Sri Lankan traders found that heating geuda to high temperatures could dissolve its rutile silk and turn it a strong blue. This changed the island's sapphire trade and is a large reason heating is so widely used today. See sapphire treatments for more.
Several famous sapphires are said to have come from Sri Lanka, including large blue stones held in museum collections and royal jewels.
Padparadscha
Padparadscha is a rare sapphire color: a delicate blend of pink and orange. The name comes from a Sinhalese word for the color of the lotus flower. Sri Lanka is the classic source, though stones from Madagascar and elsewhere are also sold under the name.
Gem labs define padparadscha within a range of pinkish-orange to orange-pink hues of light to medium tone. Stones that lean too far toward pure pink or pure orange are usually not called padparadscha. Because the color is narrow and rare, these are among the most sought-after sapphires.
Cat's eye chrysoberyl and alexandrite
Sri Lanka is a leading historic source of cat's eye chrysoberyl. Fine stones show a sharp, bright line of light across a honey-yellow or greenish body, an effect caused by parallel needle-like inclusions. When the stone is lit from one side, it can show a "milk and honey" look, with one half pale and the other half golden.
The island also produces alexandrite, the color-change variety of chrysoberyl, and some cat's eye alexandrite.
Moonstone
Sri Lanka has long been a classic source of moonstone, a feldspar that shows a floating, silvery or bluish light called adularescence. The effect comes from thin alternating layers of two feldspars inside the stone. Fine blue-sheen moonstone from Sri Lanka has been especially prized. Deposits near Meetiyagoda in the south are known for it.
Other gems
Sri Lankan gravels also yield:
- Spinel in red, pink, purple, blue and gray.
- Garnet, including hessonite and other grossular colors.
- Zircon in many colors.
- Tourmaline, topaz, aquamarine, quartz, and rare species such as taaffeite and sinhalite.
Sinhalite, a borate mineral first described from Sri Lankan material in the 1950s, is named after the island's old Sanskrit name, Sinhala.
Ancient trade
Sri Lanka's gem wealth was known in the ancient world. Greek and Roman writers referred to the island as Taprobane and mentioned its precious stones. Arab and Persian traders later called it Serendib, and Chinese and Indian records also refer to its gems. Medieval travelers, including Marco Polo, described Sri Lankan rubies and sapphires.
For centuries, the island's gems reached Europe through Indian Ocean trade routes and later through Portuguese, Dutch and British colonial trade. Today cutting is done both in Sri Lanka and abroad, with much material passing through Thailand for heating and cutting.
Frequently asked questions
What gems are found in Sri Lanka?
Sri Lanka produces blue and fancy sapphire, padparadscha, cat's eye chrysoberyl, alexandrite, moonstone, spinel, garnet, zircon, tourmaline and many rarer species. Most come from gem gravels called illam.
Why is Sri Lankan sapphire called Ceylon sapphire?
Ceylon was the island's official name through British rule and until 1972. The trade name stuck, so blue sapphire from Sri Lanka is still widely called Ceylon sapphire.
What is a padparadscha sapphire?
It is a sapphire with a delicate pink-orange or orange-pink color. The name comes from a Sinhalese word linked to the lotus flower, and Sri Lanka is the classic source.
How are gems mined in Sri Lanka?
Mostly by hand. Miners dig shallow pits down to the gem gravel layer, haul up the gravel in baskets and wash it in round wicker baskets to find the gems.