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Natural Occurrence and Processing

Diamonds are found in alluvial (loose earthy material deposited by running water) formations and in volcanic pipes, filled for most of their length with blue ground or kimberlite, an igneous rock consisting largely of serpentine. At the surface the blue ground is weathered to a clay called yellow ground. Diamantiferous (or diamondiferous), or diamond-yielding, earth is mined both by the open-pit method and by underground mining. After being removed to the surface, it is crushed and then concentrated. Sorting is done by passing the concentrated material in a stream of water over greased tables. The diamond, being largely water repellent, sticks to the grease, but the other minerals retain a film of water, which prevents them from adhering to the grease. The diamonds are then removed from the grease, cleaned, and graded for sale.

The Diamond Cartel

The discoveries of 1870-71 in South Africa led to a great number of prospectors staking out claims and securing the diamonds by open-pit or quarry mining. The damage caused by floods and mudslides, unavoidable when there were so many different claims, was an important factor in the series of amalgamations carried on by Cecil Rhodes and Barnett Barnato. Rhodes brought about the merging of their interests in the De Beers Consolidated Mines, Ltd., which established (1889) an effective monopoly over the diamond industry. Loss of diamonds by theft was reduced through the passage of the so-called I.D.B. (Illicit Diamond Buying) Act, which limited the trade to licensed buyers and imposed penalties for the possession of uncut stones without a license. Thefts were further curtailed by the institution of compounds in which the workers live while employed by the company and which they leave only after being thoroughly searched.

Diamonds are a finite resource. The fate of Indian diamonds is a good example of what the future might hold for the South African diamond-mining industry. From the first discovery of the gems in India until relatively recently, it is thought that over 12 million carats originated from India. By the mid-20th century, the resources were nearly depleted, and India was producing only about 100 carats annually. Diamonds will continue to be used in industry and high-technology enterprises, but synthetically produced facsimiles—first manufactured in 1953—may accomplish some of the tasks originally the exclusive province of the real stone. These "manufactured" gems have the same properties of hardness and durability, and while they will never be as popular as the real diamond for adomment purposes, they are well suited for industrial applications.

The Ancient World

The wearing of jewelry has very ancient roots. The oldest examples discovered to date are about 75,000 old. Found in a cave in S Africa in 2004, they consist of pea-sized pierced shell beads that were probably strung into a necklace or bracelet. Other African beads have been found dating back some 45,000 years. In the ancient world, the art of jewelry making reached an elaborate development in East Asia with its wealth of precious stones and pearls. Egyptian relics also show a rare craftsmanship. The jewelry is largely emblematic, very colorful, and displays lotus flower and scarab motifs. Beads were used extensively, as in broad collars, and were often used for bartering. Armlets and anklets were also worn.
The Greeks were highly expert goldsmiths and preferred exquisitely wrought ornaments of metal unadorned with color. After 400 B.C. precious stones were set in gold; later the cameo was used. Roman jewelry, although based on Greek and Etruscan forms, was massive and valued rather for precious stones and cameos than for artistic settings. Ropes of pearls were especially prized. Byzantine jewelry, influenced by East Asia and lavish in color and design, was of composite Greek and Roman styles.

The Middle Ages to the Seventeenth Century

Jewelry of the Middle Ages was massive; large brooches and girdles predominated. Amber was worn as a protection against evil spirits. After 1300 glass beads were used. The Renaissance brought a transformation in the art of the jeweler; noted artists and architects often designed or even rendered pieces of jewelry. Jewelry was splendid with enamel and precious stones; heavy gold link chains, jeweled collars, and the necklace with pendant were worn by both men and women. Jewelry, worn to excess, became overcrowded with stones, to the neglect of the design and setting. By the late 17th cent. the goldsmith and enameler gave way before the lapidary and mounter. A process of making imitation pearls was first discovered in 1680; thereafter, ropes of pearls became highly popular for women.

The evidence used to determine which foods were eaten by prehistoric man is scarce and can be very difficult to interpret. The majority of clues about food usage come from the study of collections of animal bones, sea-food shell mounds, plant food remnants, and faecal remains, at or close to sites of human habitation. Studies of these food left-overs provide some hints as to what foods were available to and used by prehistoric man.

Until 10-12 000 years before the present (bp), humans relied on hunting and gathering for their food. They hunted wild animals such as gazelle, antelope, and deer, as well as fish, crabs, and migratory waterfowl, and gathered foods including shell-fish, root vegetables, grains, pulses, nuts, and fruit. The period between roughly 11 000 and 6000 years bp, which has been termed the Neolithic, was a time of crucial and widespread agricultural revolution. Wild crops such as wheat and barley began to be cultivated, and wild animals such as sheep and goats were tamed and then domesticated.