The beautiful island of Sri Lanka, and home of the highest quality moonstone in the world, lies in the Indian Ocean just off the southern tip of India itself.
Gem deposits in Sri Lanka can be divided into two types – the more abundant ‘sedimentary’ deposits caused by the weathering actions of wind and water, and the less common primary deposits found within the bedrock itself.
One of the best-known primary gem deposits in Sri Lanka is the large pegmatite vein of moonstone at Meetiyagoda, a small village a few miles from the coast in the south-west of the island.
The village boasts 10 mines which have been the most important source for top quality blue moonstone since it was discovered here in 1906.
Moonstone, the most valuable of the feldspars is a sodium potassium aluminium silicate.
It consists of inter-grown layers of two varieties of feldspar with differing refractive indices – orthoclase and albite. The characteristic billowy adularescence or ‘schiller’ seen in moonstone is caused by light scattering from nanometre sized particles within these layers. The finest and rarest stones show a transparent colourless body with a strong blue schiller. Rough moonstone is extracted by shaft mining. These mines are known as ‘yati illama’ and consist of narrow rectangular shafts lined with a strong frame of coconut wood beams. As well as strengthening the walls of the shaft, these horizontal beams are fixed at equal heights allowing the miners to calculate the depth of the mine.
Kakilla leaves – a variety of fern – are applied to the walls of the shaft behind the beams. These leaves can withstand high pressure and weight and help prevent the seepage of water into the mine. The wooden frame of the mine is divided into two chambers – one is used by the miners to ascend and descend the shaft and for the removal of the ‘illama’ – the gem-bearing sludge – and the other for the electrical water pump used to keep the bottom of the mine dry.
The water that is pumped out is saved in a small reservoir where it will be used later for washing the illama.
The shaft is sunk around 20 metres through a layer of kaolin mud until it reaches the weathering surface of the pegmatite. Here the miners begin to dig out horizontal tunnels know as ‘donava’ in four directions. Each tunnel is around 10 metres long and 2.5 metres square and lined with coconut wood beams.
Once the four tunnels have been completed, the miners begin to sink the main shaft another 7.5 metres before digging a further four tunnels.
This system continues until either a maximum depth of 65 metres or the bedrock is reached.
Six miners work in each mine – three on the surface and three underground – using electric lamps and in 35oC heat.
The rough moonstone is cut from the weathered vein and brought to the surface in buckets via the main shaft using the ‘dabaraya’ system.
The dabaraya system employs a long heavy circular log placed across the mine shaft and turned by two miners in either direction via a ‘z’ shaped metal bar.
Attached to the log is a pulley system by which means a bucket on one end of a rope is raised as the bucket on the other end is lowered into the mine.
The moonstone removed from the mine is collected in a special shallow pit called the ‘illam kamatha’which is covered with a layer of the kakilla fern leaves to protect it from theft and to prevent it washing away in the rain.
Once a week – when the day is auspicious – the moonstone is washed in the reservoir under the watchful eye of the mine-owner.
A few handfuls of the gem-gravel are placed in a shallow, circular, wicker basket with a heavy rim.
The basket is lowered into the water and tilted and turned until the stones are clean.
Once washed, the moonstone rough is placed into buckets to be transported to the lapidaries for cutting and polishing.
The cutters work with both modern and traditional cutting equipment depending on personal preference.
On the whole, semi-automatic lapidary equipment is now the norm as it is quicker and in the case of faceted stones, more accurate.
However the traditional ‘hanaporuwa’cutting machine powered by a hand-operated bow-string is still the equipment of choice for cutting and polishing extremely large stones.
The vast majority of moonstone are cut en-cabochon rather than faceted. There are two forms of cabochon – the simple and the double, the latter having a slightly curved base.
Unlike other phenomenal gemstones traditionally cut en cabochon, such as cat’s eyes and star stones, the bases of moonstones are always polished.
The annual production of each mine in Meetiyagoda is around 50 kilos of rough. Around 4% of the cut stones will be the finest quality blue schiller.
All the mines are vertically integrated and concerned with all operations from the digging of the shafts to the sale of the cut and polished stones.
Proceeds from the sale of the stones are split: the landowner receives 50%, the miners, cutters and other workers divide 25% between them and the remaining 25% covers overheads.
The small-scale of mining and lack of mechanisation – a deliberate action on the part of successive Sri Lanka governments – means that the industry in Meetiyagoda is both sustainable and has a minimal impact on the environment.
Despite many reports that top quality blue moonstone is now mined-out, the truth is that it will still be produced in Meetiyagoda for some time to come.