Chapter 9

Diamonds and Diamond Industry of Sri Lanka

The introduction of diamond cutting and trading into Sri Lanka is a significant achievement for the whole country. The history of the country's gem industry reveals that for a thousand years the trade was mainly dominated by sapphires and rubies plus a number of other gemstones. Today, the Sri Lanka gem industry has taken another step ahead with the establishment of a major diamond cutting centre in Southeast Asia.

At present there are some 15 private organisations, some of which are joint ventures with foreign companies. The main area of activity is cutting imported rough diamonds, which are then exported. Some cut diamonds are however, used in jewellery manufactured in Sri Lanka. As the diamond industry is new to Sri Lanka, and information regarding this industry may not be readily available, some background information may be of interest to the reader.

General introduction

The word 'diamond' is from the Greek adamas meaning unconquerable. The stone was so called because it cannot be cut by any other substance.

India is the first country known to have produced diamonds. It is reported that the first discovery of diamonds was in the region of Golconda, near Hyderabad over 2000 years ago. In modern times, Australia, Botswana, Russia, South Africa and Zaire are the leading countries in the large scale production of diamonds. In 1725, when the diamond reserves of India were becoming exhausted, diamonds were discovered in Brazil. For a century Brazil remained the major source of diamonds. However, in 1866 diamonds were discovered in South Africa and it in turn, became the main supplier. Today, Australia is the world's leading producer of diamonds in a volume, producing almost one third (33%) of the world's total production. Apart from Australia, the other three leading producers in terms of production volumes are Botswana, Russia and Zaire. Other notable producers include Angola, Brazil, Namibia and to a lesser extent Sierra Leone and Tanzania.

Occasionally exceptionally large diamonds are found. The world's largest polished diamond so far discovered is the 'unnamed Brown' of golden brown colour, weighing 545.67 carats. The original rough weight of this diamond was 755.50 carats and when cut, yielded about 70% of its weight. It is recorded that the rough stone of the 'unnamed Brown' was found at the same time as the 'Centenary' in the Premier Mine.

The largest rough diamond so far discovered was the 'Cullinan'. This stone was found in the Premier Mine in South Africa, and weighed 3,106 carats. The rough stone was cut to produce 105 cut diamonds, the largest of which weighed 530.22 carats. This is called the 'Great Star of Africa'. It is at present one of the Crown Jewels of Great Britain.

The second largest rough diamond found, was the 'Excelsior' from the Jagersfontain Mine in South Africa, weighing 972.9 carats. In 1972 another large diamond weighting 968.9 carats, name "Star of Sierra Leone' was found in South Africa, which is the third largest rough diamond ever to be discovered.

In 1986 another famous diamond, known as the 'Centenary' was discovered in the Premier Mine in South Africa. The rough stone, which weighed 599 carats, produced 273 carats after having been cut and polished and is the only significant diamonds cut by De Beers (now called The Diamond Trading Company). According to the De Beers its insurance value is U.S.$ 100 million.

Genesis of diamonds

The usual source of diamonds is kimberlite pipes, which were first discovered in South Africa. Kimberlite pipes are vertical or nearly vertical, roughly circular volcanic intrusions consisting of igneous rock rich in olivine. When kimberlite is exposed to the atmosphere, it turns into soft blue mud, called 'blue ground'.

The primary sources of diamonds, occurs in old continental rocks called cratons. These cratons are places where the continental crust is particularly thick, up to 30 kilometres.

Diamonds are formed or crystallised under enormous pressures and temperatures. This means that diamonds are created by at great depth within the Earth, in a region beneath the crust known as the mantle.

Diamonds are brought to the Earth's surface by molten magma, that originates at great depths. The rock is called the kimberlite after the city of Kimberly in South Africa where it was first discovered in the 1870's. Another rock type that provides diamonds is called lamproite. Kimberlite can be thought of as an express elevator bringing the diamonds from the mantle to the surface, where people can find them. Although rising from much greater depths than other magmas, these pipes and volcanic cones are relatively small and rare, but they erupted in extraordinary supersonic explosions. Kimberlite and lamproite are similar mixtures of rock material. Their important constituents include fragments of rocks from Earth's mantle, large crystals and the crystallized magma that glues the mixture together. The magmas are very rich in magnesium and volatile compounds such as water and carbon dioxide. When the volatiles dissolved in the magma change to gas near the Earth's surface, explosive eruptions create the characteristic carrot or bowl shaped pipes.

Properties of diamonds

Diamond is a mineral composed of pure carbon which has crystallised deep in the earth under enormous pressure and temperature. Today, the western world regards cut diamonds as a symbol of love. The extraordinary properties of this nature's gift make its very existence something of a miracle. On average, 250 tons of kimberlite will produce one carat of gem quality diamonds. This may contribute to the reason why diamonds are regarded as the most precious and valued gem in the world.

Diamond is by far the hardest substance in the mineral kingdom (possessing the value of 10 on the Mohs' scale of hardness). Diamonds are found in wide range of sizes and shapes. In nature, diamonds are commonly found as octahedrons, although occasionally cube-shaped diamonds are found.

Diamond is found many colours. Colourless diamonds are most commonly encountered in the diamond trade, but they are also found in yellow, brown, red, pink, blue, black and green.

Diamonds are known for their brilliance and 'fire'. They also possess an exceptionally high luster, known as 'adamantine'. The beauty produced by these properties may exceed even that of the Sri Lanka's most valuable and attractive gemstone, namely the blue sapphire. Diamond has a specific gravity of 3.52, its refractive index is 2.417 and it is singly refracting. Diamonds are transparent to X-rays.

Diamond cutting and polishing

The cutting and polishing of diamonds can be hard, complicated and costly process. Although diamonds are now often cut by laser, only diamonds and diamond powder can be used to cut another diamond.

Even though the hardest material on the Mohs's scale is diamond, a phosphor bronze disc impregnated with diamond powder can be used to cut a diamond. Diamond, like wood, has grain. It can be split along a plane of cleavage, or sawn against it.

Diamond cutting tools are generally expensive and specialised. The phosphor bronze disc used for diamond sawing rotates at an enormous speed of about 8,000 - 9,000 r.p.m. which is considerably faster than discs used for cutting other gems.

Before the cutting and polishing process begins, it may be necessary to cleave or saw the rough diamond. Once a rough diamond is cleaved, it is then re-examined for any further necessary sawing before it is passed on to the polishing process.

The machine used for diamond polishing is very specialised. The most important part of the diamond polishing process is the use of a high speed revolving horizontal wheel called a scaife. It is made of cast iron, about 25cm in diameter and about 10mm. thick. It rotates between 2800 - 3000 r.p.m. The surface is impregnated with diamond dust which does the actual polishing.

Diamonds can be cut to various shapes and sizes. Different diamond cuts include pear, heart, marquise, baguette and princess cut. However, the most popular diamond cut is the standard round brilliant cut which has a total number of 57 or 58 facets (depending on whether the 'culet', or point of the diamond is polished).

The Diamond Trading Company (DTC)

The Diamond Trading Company is famous world-wide for its diamond trade. Around 50% of the world's diamonds are marketed by the DTC, mostly through London. The DTC is a division of the De Beers group and was established in 1934.

The main activities of the DTC include the sorting, valuing and selling of unpolished (rough) diamonds, as well as the marketing of polished diamond jewellery. At various DTC offices, diamond sorters carry out the major classification of rough diamonds. The DTC has diamond sorting offices in South Africa, Namibia, Botswana and the UK. In addition, the company has marketing offices in many of the world's major diamond markets, including India, Japan, Dubai, Hong Kong and Italy.

The diamonds sold by the DTC are purchased by a group of clients, known as Sightholders, who are selected on the strength of their marketing skills, diamond cutting abilities, ethical business practices and other objective criteria.

Classification of rough diamonds

The classification of rough diamonds is one of the most fundamental priorities in the diamond industry. Diamonds are classified according to a systematic scale before being sold. At DTC rough diamonds are sorted into over 14,000 individual categories.

DTC uses rough diamonds for classification based on sets of master-samples using their own terminology.

The first step in the classification of rough diamonds, is to divide them into gem and industrial stones. The gem quality diamonds are then sorted into further grades on the basis of their shape, quality, colour and size.

Medium to large-size rough diamonds are sorted on basis of shape into six classes. From the most acceptable to the least, these are called: stone, shape, cleavage, maccle, flat and cube. As an example'stone' implies a shape approximating an octahedron. This shape is considered to be the best because it is the most economical to cut.

Smaller rough diamonds are simply classified as being either'sawable' (nice shaped models) or 'makeable' (irregular models).

The quality, sometimes known as clarity, of rough diamonds is determined by the amount of imperfections or inclusions within the diamond. The absence of inclusions upgrades a diamond. Other factors affecting the clarity are the number, position and size of these inclusions.

Colour grading which is done by using a series of master colour samples. Pure white or colourless diamonds are considered to be the best, while tinted diamonds are graded into their own different

categories.

After the classification of the rough diamonds is completed, they are sealed into individual packets and placed into 'boxes'. Selected buyers are invited to a'sight' to examine the boxes. Around 160 buyers, mainly cutters, jewellery manufacturers and some dealers, are invited by DTC to attend ten sights or sales each year. At the sight DTC offers a selection of stones which match as closely as possible to the buyers' requirements based on the requests made in advance.

Diamonds at the sights are sold at fixed prices. Each buyer is represented by a broker who is there to act on his behalf.

The majority of buyers invited are from New York, Antwerp, Israel and India, others are from the Far East, including Sri Lanka.

Classification of cut diamonds

Cut diamonds are classified in a manner similar to the rough material. It is carried out on the basis of four characteristics, generally called the 4Cs:

1) Colour

2) Clarity

3) Cut

4) Carat-weight

Of these, the first three, colour, clarity and cut, are considered the most important factors.

Colour

Cut and polished diamonds are graded according to the international rules of colour grading.

There are different scales of colour grading established in various countries and by various organisations. The most important colour grading systems frequently used include the Gemmological Institute of America (GIA) and the International Confederation of Jewellery, Silverware, Diamonds, Pearls and Stones (CIBJO). The following colour grading classifications introduced by the CIBJO and GIA are well known internationally and most commonly used in the diamond industry today.
