Diamond

Early in 1867, on a farm near Hopetown on the Orange River, a boy called Erasmus Jacobs picked up a shiny pebble and added it to the stones he and the other children played with. His mother showed it to a neighbour, Schalk van Niekerk, who passed it on to people who might know what it was. In Colesberg, the civil commissioner found it would scratch glass. In Grahamstown, Dr W. G. Atherstone pronounced it a diamond of 21.25 carats. It became known as the Eureka.

Nobody had thought to look for diamonds in South Africa until then. Within two years the river diggings had produced hundreds of them, among them the 83.5-carat Star of South Africa. That pebble is where the modern diamond story begins, and why a diamond is the first of our Big Five.

From the river to Kimberley

In 1870 diggers began finding diamonds well away from the rivers, on farms in the "dry diggings". These were later understood to be the weathered tops of ancient volcanic pipes, and thousands of people from many countries rushed in to stake claims. The town that grew up there was Kimberley, and the rock that carries diamonds up from deep inside the earth is still called kimberlite, after it.

The largest diamond ever found

In 1905 a diamond of more than 3,000 carats was found near Pretoria. Named the Cullinan, it is the largest diamond ever discovered. In 1907 it was presented to King Edward VII, and Asscher of Amsterdam cut nine large stones from it. The largest, Cullinan I, the Star of Africa, weighs 530.2 carats and is set in the British Sovereign's Sceptre. It is still the largest colourless cut diamond in the world.

Beliefs and legends

Nearly two thousand years ago, the Roman writer Pliny the Elder called diamond the most valuable of all things in the world, not only of precious stones.

What it is

Diamond is pure carbon, crystallised under enormous heat and pressure far below the earth's surface. It is the hardest natural material known, 10 on the Mohs scale. That hardness lets it take a razor-sharp polish, and the way it bends light gives it a brilliance and fire no other colourless natural stone quite matches.

The four Cs

• Cut decides how well a diamond sparkles. A well-cut stone returns light across its whole face; a poorly cut one looks glassy or dark in the centre, whatever its other grades.
• Colour in white diamonds runs from colourless to faint yellow. Neighbouring grades are very hard to tell apart once the stone is set.
• Clarity measures inclusions. Most are invisible to the eye; what matters is a stone that looks clean to you.
• Carat is weight, not size. Two stones of the same weight can look different sizes, depending on the cut.

Honesty about diamonds

When we say "diamond", we mean a natural diamond. Laboratory-grown diamonds usually cannot be told apart from natural ones without laboratory testing, which is why we name exactly what you are buying. Some of our diamonds are GIA-graded or EGL-graded; when the stone you are looking at has a grading report, ask to see it.

Caring for your diamond

Diamond scratches almost anything, including other diamonds, so store pieces apart. It can still chip from a hard knock on an edge. Clean it in warm water with a little washing-up liquid and a soft brush: grease dulls a diamond quickly, and a clean one sparkles noticeably more. Have the claws checked once a year.

At a glance