diamond processing and sorting

8/3/2019 Diamond Processing and Sorting

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Diamond Processing and Sorting

After diamond ore is mined it is transported to a processing plant where it is first fed intohuge crushing machines. In the old days diamonds were recovered on vibrating greased tables.

After the diamond ore was crushed it was mixed with water and slid down the table. Because oftheir surface properties, rough diamonds adhere tenaciously to the grease while other materialsvibrate on through.

Now the crushed rock is moved on a conveyor belt through a darkened chamber and X-rayed. Photo sensor detect the diamond's fluorescence and air jets remove it. Workers then sortthe gem quality stones from the industrial diamonds by hand.

Gem quality stones are sorted further in the large sorting room at the De Beers headquartersin London. On observing the sorting of five weeks of the worlds production of gem diamondsbetween two and nine carats in this sorting room, Fred Ward wrote in National Geographic, "Iwas dazzled with the brilliance of tens of thousands of uncut diamonds. On the counter runningthe length of the building, keen-eyed workers faced north windows for the indirect, even-colorlight needed to sort piles of roughs. Eight central tables were laden with sparkling crystals.

A DeBeers official told Ward, There are about 180,000 carats on those tables, worth about70 million dollars. When we have all the stone together for next month's 'sight' or sale, includingvery small stones and stones over 100 carats, they will bring 250 million.

Diamond Cutting

Diamond cutters are called lapidarists. Their goal is to get as large and as beautiful a gem aspossible from a rough stone without losing too much material. To achieve this goal theyessentially use the same techniques they have for the last 600 years. Lapidarist are very careful.They may study a diamond for months before working on it. Student diamond cutter who maketwo major mistakes fail to get certified.

Diamonds can be cut several ways: 1) cleaving, in which the diamond is split with a chisel,is relatively rare these days; 2) sawing with a circular copper blade embedded with diamond dust

particles; 3) grinding by pressing the diamond against a covered diamond-dust-covered steelwheel (called a skive) that spins at 3,000 rpms.

Even though diamonds are quite hard they are relatively easy to cut along cleavage lines intheir crystalline structure. The only thing that will cut a diamond is another diamond. Theadvantage of sawing over grinding is that sawing leaves behind saleable pieces of diamondswhile grinding produces only dust. grounded stones never touch the wheel. They are pressed


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close but kept away slightly with a layer of oil. Diamond will shatter so great pains are taken tomake sure this doesn't happen. They Lapidarists are especially wary of inclusions (black spots)which cause a diamond to crack.

Most diamonds give a yield of 40 to 45 percent from rough to polished stone using currentmethods. Sometimes as much as 70 percent of a diamond is lost during the cutting and polishingprocess, but the price can jump six fold. The 1977 price for colorless 2 carat rough wasUS$750. A flawless one carat stone can fetch as much as US$20,000.

Types of Diamond Cuts

Technology for faceting gems was not invented until the mid-17th century. The round idealis the standard cut. Developed in 1919 by a mathematician and diamond cutter, Marcel Tokosky,as part of his doctoral dissertation at the University of London, it has 58 facets and was designed

to highlight a diamond's light refraction and maximize its brilliance and fire. The Brilliant cut issimilar (the same???). It is the most popular shape.

Other popular cuts include the Emerald, marquise, and pear. New cuts include the Hearts ofFire, similar to the round ideal except the 58 facets are precisely aligned and polished and revealsa symmetrical heart and arrow when magnified; the Eternal, an 81-facet pedal design introducedin 1999; and the Leo, a 66-facet cut designed to bring out the brilliance.

The Gemological Institute of America has devised software to enable retailers andconsumers to compare diamonds of different cuts by grading the cut automatically.

In most cases, large diamonds are sawed first along lines drawn on it with India ink,grounded and then polished. In 1978, a fist-size 341.9 carat diamond was cut in Belgium usingsuch methods. It took six weeks to cut through the inch and three quarters stone.

The largest flawless oval-cut diamond in history, a 102.23-carat stone, was cut from a265.82-carat diamond found in Zaire along with four large diamonds by master cutter MottiBernstein. When asked about his work, Bernstein said, "When I cut a diamond I dont thinkabout value; otherwise I get nervous." The value of the 102-carat stone has not been revealed.

Another diamondthis one 22-caratscut from the Congolese stone ended up a with another22-carat diamond on a necklace for $3.5 million.

Diamond Cutting and Grading Technology


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Some diamond cutters now use computer-driven machines with robot arms that can cut 24diamonds at the same time. Diamond cutters use computer programs with three-dimensionalimages to determine the most profitable cuts.

In recent years lasers have been introduced that make rough cuts and carry out bruting thebeveling process used to give diamonds their characteristic sharp-edges shapes. CalibratedDiamonds of Johannesburg is developing an automated laser-cutting system The system canmake more precise cuts and even polish diamonds.

Researchers at Cambridge Universitys Institute of Manufacturing claims they have deviseda system that can accurately and consistently grade diamonds and other gems based on clarity.The system, called iGem, works out the value of a rough diamond and suggests ways to cut thestone to maximize value Based on the judgments of four diamond experts who classified 503virtual stones, computer models of stones with different kinds of flaws was devised and set ofclear rules were established. Gems that are scanned using a desktop X-ray tomography machineand rated according to the system. If a stone falls somewhere in a grey area between ratings , asystem kicks that suggest ways to improve the stones value tests by iGem show that followingits rile sit could increase the value of a stone by as much as 23 percent.

Diamond Cutting and Polishing Business

Belgium has traditionally been the center of the diamond cutting and polishing trade. Thetrade for rough and polished stones revived in Belgium after World War II but the crafts ofcutting and polishing moved from Belgium to India, Thailand and Israel. There are also largenumbers of cutters in Vietnam and Sri Lanka.

Most of the stones cut and polished in India are small. The larger stones are cut primarily inBelgium. The worlds largest diamond, the Cullinan, was cleaved by the famous diamond cutterJoseph Asscher, who studied the stone for six month before dividing it into two pieces. After hestruck the famous diamond, successfully dividing it the way he wanted, he reportedly fainted andcollapsed on the floor of his workshop.

Antonio Blanco was one of the most famous diamond cutters in New York Citys Diamond

District. His masterpiece was a 100-carat yellow diamond called the Dream that was valued at$20 million. He died in 2009.

Diamond Cutting and Polishing Business in Belgium

Antwerp is still regarded as world's diamond trading and cutting capital for big stones. Onethird of De Beers buyers are found here and they reportedly account for 60 percent of all


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diamond transactions. The diamond trade accounts for $4 billion a year and 6 percent ofBelgium's total exports. In the 1990s about 16.8 percent of all polished diamonds imported intothe United States came from Belgium by weight of carats and 27.4 percent by value in dollars

Antwerp accounts for over 40 percent of the world's diamond cutting and polishing and 60percent of the trading of large diamonds. Many of the diamonds that originate in southern Africapass through here on their way from the mines to the jewelry stores; arriving here as raw anduncut stones and leaving as marvelous multi-faceted gems.

The first documented diamond deal in Antwerp was recorded in 1447 but the industry didn'ttake hold into the 19th century when Ashkenazi Jews arrived from Central Europe and built upthe city's diamond exchange. The Jewish population of Antwerp dropped from 50,000 to 800during the Holocaust. The trade for rough and polished stones revived after World War II but thecrafts of cutting and polishing moved from Belgium to India, Thailand and Israel. The number ofdiamond workers declined from 19,000 in 1968 to less than 3,500 today.

Most of the world's uncut stones are traded from diamond exchanges in London andAntwerp. Hasidic Jews and dealers from India, South Africa, Zaire and Lebanon walk the streetson Antwerp. The Diamond Exchange in Antwerp has vaulted ceiling windows because beforethe advent of fluorescent lamps diamantaires only trusted natural light.

Antwerp is also known as the center of the diamond black market. Thieves often come hereto sell their stones. Buyers purchase them as off the books investments. The appeal of diamondsis that they small, easy to concealyou can walk around with a million dollars in the your

pocket and that much money in diamonds is much easier to hide and more difficult to trace thancash. [Source: Fred Ward, National Geographic, January 1979 []

Diamond cutters in Antwerp specialize in cutting stones with odd shapes. Belgian craftsmanare known for their unsurpassed skill and the largest diamonds in the world have been cut inAntwerp. Cutters use diamond dust and olive oil on their saws.

P.N. Ferstenberg was honored with the title "Dean of the Diamond Industry" by the BelgianGovernment, the diamond industry and the diamond workers. As the title clearly indicates he

gets on well with most every one. Still he caries a large automatic weapon in his pocket. "Withdiamonds" he said, "you can not be too careful.*

Diamond Cutting and Polishing Business in India

India is the world largest diamonds and gemstone cutting center. At one time it polished andcutting around 70 percent of the world diamonds as determined by weight. Centered in the


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western cities of Bombay and Surat, the diamond industry provided India with 17 percent of itsexport earnings in the 1990s. These days India is getting more and more competition from Chinaand Thailand.

The diamond industry produced $8 billion worth of exports in the 1990s. Gujarat state inwestern India is the major diamond processing and cutting center. About 90 percent of theindustry is based in Surat in Gujarat. Bombay is major diamond trading center. The heart of thediamond trading business is in the Opera House District of Bombay.

The Indian diamond industry traces its origins back to the 1970s when a group of Jains setup an operation in Bombay and began to cut very small diamonds for export. They are creditedwith creating a market of small gems from industrial diamonds. The amount of processeddiamonds rose from $39 million in 1970 to $3.5 billion in 1993. India held about 45 percent ofthe worlds' market in cut and polished diamonds in 1990. Lead by phenomenal growth in theexport market, the country share rose to 70 percent in 1997.

The Indian diamond business is dominated by a handful of Jain families, which have beeninvolved in the trading of pearls and precious stones for centuries. Most of the diamonds aresupplied by the Rio Tinto-controlled Argyle mine in Western Australia and by South-Africabased De Beers, the world's largest player in the diamond trade. Most of the stones cut andpolished in India are small. The larger stones are cut primarily in Belgium.

Diamond Workers

Most diamonds are cut in India, China, and Thailand, where skilled labor is cheap. Thediamond industry in India employs about 800,000 people in its cutting, polishing and exportingoperations. Many of them work 10-hour days at plants in Surat for $80 a week. About 10 to 20percent of the workers are children, many of whom eat and sleep in their workplace.

Working for a total of three hours, three workers make a "round brilliant" diamond with 58-facets that their company sells for less than $1 a piece and can fit into a pit on a strawberry.

Indian diamond cutters and polishers have traditionally used cutters wheels in poorly light

sheds, where they lived and worked. Some of these sweatshops have been replaced by brightly-lit factories with modern lathes and power driven cutting tools. Some craftsmen are highlyskilled: stones weighing a fraction of a carat into polished gems.

Diamond cutting and polishing is not a very glamorous business. Half the workforce inIndia suffers from kidney disfunction, tuberculosis, lung disease, stomach problems, pain in thejoints and sore eyes. It can also be dangerous work. In August 2003, a gas cylinder exploded at a


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diamond processing factory. The fore spread to a residential building and 19 people were killedand 36 were injured.

India and Israel Compete in the Diamond Business

India is competition with Israel in the diamond production and cutting market. Israel hastraditionally processed high quality stones, while India specialized in lower grade diamonds.About 59 percent of all polished diamonds imported into the United States come from India, and20 percent from Israel. The average price for a diamond imported from India was $219 a carat inthe early 1990s, compared to $817 a carat from Israel. [Source: Sanjoy Hazarika, New YorkTimes, August 24, 1994]

In the future India is planning to make a move into Israel's market. "While India has theadvantage of low wages," wrote Sanjoy Hazarika of the New York Times, " Israel is offsetting

this by mechanizing its polishing and cutting operations. Like Israel, India mines virtually nodiamonds of its own and imports most of its uncut stones from diamond exchanges in Londonand Antwerp, Belgium.

Diamond Cutting and Polishing Business in Israel

Israel once dominated the diamond processing market. It exported $2.5 billion in processedstones in 1993. Tel Aviv is major diamond trading and cutting center. The heart of the diamondbusiness is in the high rise district of Ramat Gan. Multi-million dollar diamond deals are basedon trust. There is no contract. "We say mazal tov , good luck," a Tel Aviv merchant told National

Geographic, "and that seals the bargain."

Israel is the leader in the sales and cutting of diamonds less than a carat and it accounts forhalf the world's caratage. Automatic polishing machines in Tel Aviv can work on four stones at atime and each machine churns out 1200 eight point (8/100 of a carat) diamonds a day. Diamond'sare Israel's largest export, generating over a billion dollars in hard currency for a country thatalways seems to be strapped for cash. Most of the stones end up in jewelry with multiplesettings.

The diamond industry employs about four percent of the national work force, and produces40 percent of the country's exports. The expertise for the Israeli diamond came mainly fromEuropean cities such as Antwerp and Amsterdam which were known as the diamond capitals ofthe world before World War II.

Image Sources: 1) 2) 3) 4) 5) 6) 7) 8)

Text Sources: Mostly National Geographic articles. Also the New York Times, Washington Post,Los Angeles Times, Wikipedia, The Independent, Times of London, The New Yorker, Time,


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Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Comptons Encyclopedia and variousbooks and other publications.

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