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GEMSTONE MINING
Gemstone Deposits
A deposit is defined as a group of occurrences large enough to be worked (also called a mine). A find is described as a single occurrence.
 
Primary deposits refer to gems found in their original location. The yield is generally low due to the fact that many tons of non-gem bearing material has to be excavated.
 
Secondary deposits refer to gems which have been transported by the actions of wind, rain and flowing water.
 
Fluvial deposits are created by rivers, marine deposits by the sea and Aeolian Deposits by the wind.
 
Mining Methods
Most gemstones are discovered by accident. There is no systematic approach used for Coloured Gemstones due to the lack of capital. Australia is exceptions, where the mining of Sapphires is more mechanized and systematic.
 
They consist of:-
Collecting gems from the surface, from dry river beds, or rock fissures.
Sinking shafts into the ground sometimes up to 30ft deep.
Panning rivers.
Driving short tunnels into the sides of hillsides (used for mining Ruby, Sapphire in Mayanmar and Emerald in Colombia)
Open-cast mining (i.e. Ammolite)
Using powerful jets of water, when available, to loosen the gem material from the overburden.
Digging pits into ancient river beds to reach the "Gem Gravels", (i.e. Sri Lanka, Mayanmar, Thailand).
Terrace mining (i.e. The Chivor Mine in Colombia).
Underground mining which is expensive and can only be justified if a significant vein is located.
 
Famous International Gem Mines
Sri Lanka
Sri Lanka is situated in the Indian Ocean south-west of India. It is bordered by the Indian Ocean to the north, south, east and west. It is located a few degrees north of the equator and is the 24th largest island covering some 25,332 square miles.
 
The population is approximately 14 million comprising of 79% Sinhalese, 13% Tamil (both South Indian & Sri Lankan Tamils) and 7% Moors.
 
Sri Lanka was formerly known as Ceylon until May 22nd, 1972.
 
Ceylon is the ancient Sinhalese name meaning "Resplendent Land”, also known as SERENDIB or TRAPROBANE to ancient navigators.
 
The climate and vegetation are both tropical. Warm and humid at sea level (average temperatures 78 F to 82 F); the humidity during the day can be 70% (at night 90%). In the mountainous regions, average temperatures are 60 F. The monsoon seasons are from May through June and September through November. Average rainfall varies from below 40 inches in the dry northern zone and on the eastern slopes of the mountains to over 200 inches in some places on the south-western slopes. March to April is the hottest months.
 
Sri Lanka is an important source for not only gems but also tea, spices, rubber and coconuts. Approximately 2/3rds of the cultivated land and 2/3rds of the population are involved in the production and distribution of these products. Tea, rubber, coconuts and rice make up 95% of the countries exports and account for 75% of the cultivated land. Tea brings in over 66% of the yearly income from exports. In fact, Sri Lanka is the second largest producer of tea.
 
Rubber accounts for 15% of the yearly export income and coconuts account for 14%.
 
Gems continue to be a small and significant product of Sri
 
Lanka and has supplied the world with fine Rubies and Sapphires for over 2,000 years. Many consider Sri Lanka to be the original source of Ruby and Sapphire.
 
Although Burma has produced finer qualities, Sri Lanka has produced Rubies and Sapphires in larger sizes for longer periods of time.
 
All varieties of Corundum are found in Sri Lanka including the "PADPARADSCHA" which is unique to the island.
 
Main Gem Centers of Sri Lanka
Ratnapura: The oldest known source in Sri Lanka, meaning "City of Rubies" or "City of Gems".
Elehara District: important in recent years for producing large and fine specimens of many gems including Sapphire and Cat's Eye Chrysoberyl.
Area around Morawaka: known for Alexandrite and Cat's Eye Chrysoberyl.
Nuwara Eliya: situated in the mountainous tea country.
 
Mining
Mining in Sri Lanka is mainly alluvial with gem deposits found not only in present river systems but also below rice paddies where ancient rivers once flowed.
 
The depth of the gem gravel or "ILLAM" varies from 3m to 20m to as much as 40m at Pelmadulla.
 
The search for gems is a highly speculative operation and is usually carried out by a group of native workmen on a share basis. 1/5th goes to the owner of the land, 1/5th to the financier and the rest goes to the workers.
 
Access to these gem producing areas is often limited especially during the monsoon seasons. When the word spreads that a miner has struck paydirt, the area is soon inhabited by treasure seekers who dig pits everywhere. These pits are usually dug very close together with somewhat thin retaining walls between them. Pits can be up to 50 feet deep and are hazardous at night to both humans and animals. Deserted pits, left with standing water, become breeding grounds for mosquitoes and the resulting malaria is constantly challenging the local governments.
 
Pits are normally worked by 4 workers, one to fill the baskets with "ILLAM", one to throw it to the top, one to catch it and one to take it to the washing area.
 
Water is a big problem especially with the high water table that some areas have. It must be constantly bailed or pumped out using petrol-operated pumps since by law, only the simplest of equipment is allowed in Sri Lanka. Only in areas slated to be submerged due to the construction of large dams for hydro-electric projects has the government allowed modern mining methods.
 
Although the many restrictions have hindered the progress of the gem industry in Sri Lanka, it has provided prolonged employment for thousands of needy villagers.
 
Once the gem gravel reaches the central washing area, it is emptied into deep conical baskets which are large enough to wash approximately 20 basketfuls of illam at a time.
 
The art of washing is reminiscent of panning for gold with the water carrying the mud and lighter stones through the fine mesh and over the top of the basket. This leaves the heavier materials clean and concentrated at the bottom of the cone.
 
The sorting is carried out by one who is expert in the recognition of rough gems. First the larger fine precious stones are removed (known as JATHI) and given to the financier of the project for safekeeping. The residual (known as TOURA-MALI) is handed to another man to ensure that nothing has been missed.
 
The Sri Lankan gem gravels also produce zircon, tourmaline, peridot, quartz, garnet, feldspar and a number of other stones. Diamonds, opal and emerald are not found on the island.
 
Thailand
Thailand is bordered by Mayanmar and Laos to the north, Laos and Cambodia and the Gulf of Siam to the east, Malaysia to the south and the Andaman Sea and Burma to the west.
 
It was formerly known as Siam until 1939 when it became known as Thailand.
 
Allied to the Japanese in the Second World War, the name was abandoned in 1945 by the pro-allied free Thai government to expediate peace negotiations with Britain but was revived in 1948.
 
Although Thailand has been a constitutional monarchy since 1932, political power long resided with the military regime.
 
In 1973, the military regime of KITTIKACHORN was overthrown by student uprising and replaced by a civilian government in 1975.
 
Thailand covers some 514,000 square kilometres. Its population is approximately 55.5 million. The capital is Bangkok.
 
Thailand is unique in that it is the regions only nation to have avoided the experience of colonial domination and has therefore been able to preserve much of its traditional society, religious traditions and ancient India-derived conception of governmental authority.
 
The climate is hot and humid most of the year. In the central valley, temperatures rarely go below 65 F in the coolest months (December / January) and extend upward to around 100 F from March to May.
 
The rainy season extends from June through September. The central valley lies in the rain shadow of the Mayanmar Mountains to the west and receives annual precipitation of 40 inches compared to 220 inches in Mayanmar. The vegetation is tropical.
 
Gem quality Corundum is found at three major localities in Thailand and neighbouring Cambodia.
 
Gem Localities
Chanthaburi, Trat, Pailin
Khao Ploi Waen: thought to be the first place in Thailand where Corundum was found.
Bang Kha Cha Gems Found : Blue, green, yellow and black star Sapphires
Bo Waen : Ruby only
Bo Na Wong : Ruby only
Wat Tok Phrom : Ruby only
Ban Bo I-Ram : Very deep Blue Sapphire
Nong Bon : Ruby - larger stones
Bon Rai : Ruby - finer colours
Pailin Fields : Ruby
 
Bo Ploi, Kanchanaburi
It is considered to be Thailand's major source of Blue Sapphires.
It was discovered in 1919 and also produces the occasional yellow, pink and star Sapphires.
The Blue Sapphires strongly resemble the heat-treated blue sapphires from Sri Lanka. Most are sold in parcels of Sri Lankan goods because of the preference for Sri Lankan blue sapphires.
 
Mining
There are two types of mining in Thailand.
Primitive Pit Mining
Mechanized Mining
 
As a general rule, access is limited into many of the gem producing areas. At BO WAEN, BO NA WONG, WAT TOK and BAN BO I-RAM, access is very poor although a number of large mechanized mines are found. At NONG BON and BO RAI access is good and it is at these two sites, where Thailand's largest mines can be found.
 
In the dry season, the roads are extremely dry and dusty but during the rainy season, the roads become almost impassable except by four-wheel drive. In some cases, the mud can be several feet deep and often crudely built bridges are washed away during the summer rains.
 
Most of the mining in the Chanthaburi area is alluvial. If gem indications are found, the jungle can be uprooted and cleared in a matter of days. What remains is an open clay field where gems may be found at depths of only 3 to 5 feet.
 
When gems are found, local villages spring up quickly with housing made of regional timber and tin roofs to protect against the monsoons. Many houses are not enclosed within walls. Digging, washing and sorting are all carried out in the backyards.
 
Generally, one worker will remove the earth at the bottom of the pit and another will man a bamboo lift which brings the earth to the surface. After sufficient quantities have been brought to the surface, the earth is placed in either bamboo trays (similar to Sri Lanka) and washed in small man-made pools or placed in large sluice boxes, screened at one end. High pressure water is forced onto the gravel, washing away the loose clay which runs as mud and water through the screens. Washing may take up to an hour leaving pure gravel behind.
 
As the gravel is sorted, the sorter usually puts the gems into his mouth and when his mouth is full or the basket is empty, they are put into parcels. Sometimes they are put into plastic bags filled with water to intensify the colour and magnify the size to potential buyers.
 
A more costly venture in a major producing area is the use of a bulldozer. Using this method, the jungle and overburden can be stripped in a matter of hours. The remaining soft clay can then be eroded away using powerful water hoses and the resulting mud is "vacuumed" away by the second miner and directed towards the sluice boxes.
 
The mud is then filtered through the screens built into the bottom of the sluice boxes leaving the gem gravel behind.
 
Chanthaburi is famous for its household industry in the cutting and polishing of gems. These include not only locally mined gems but also gems from around the world. Almost every home has a grinding wheel and one or more polishing wheels. Both hand and power driven machines are used.
 
After the preforming has been done, the final polish is placed on the stones. The stones are "dopped" and propped against a make-shift ledge with all the angles and finished polish estimated by the naked eye.
 
 
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