Our next publication in the "Stone of the Month" column is about the October diamond, a precious stone that has been given a faceted shape through treatment that brings out its natural brilliance to the maximum.

If we are talking about a stone in a piece of jewellery, it is called a diamond. If we are simply talking about a natural mineral, we call it a rough diamond. Diamond is a mineral that is almost 100 per cent carbon with a small amount of various inclusions. The main characteristic of a diamond is its "absolute" and invincible hardness, which is the highest on the Mohs scale* at 10. It is the physical properties that make the difference. Once cut, the stone begins to literally shine. The secret lies in the refraction of light rays hitting the numerous facets.

Diamonds originated deep in the in the interior of the earth hundreds of millions years ago. Under tremendous pressure and at very high temperatures, carbon atoms formed a diamond crystal, and the eruption of ancient volcanoes brought it close to the earth surface where people could find it.

In all languages, the word "diamond" is associated with strength and power. Because of its bright lustre, other optical effects and high hardness, a diamond (rough diamond) is rightly considered the king among all gemstones.

Diamonds were discovered by man quite a long time ago - as far back as the 4th millennium BC. They were found in India. According to historical data, these stones were considered valuable by the ancient Romans. But the Europeans discovered the beauty of diamonds later -- in the 5th-6th centuries BC.

Up until the 18^th century, diamonds were mined in India and on the island of Borneo. Most of the historically famous diamonds come from there. For example, Koh-i-Noor, Sancy and Regent diamonds, Shah diamond, Orlov (Great Mogul) diamond, the Hope diamond, the Dresden Green Diamond are of Indian origin.

A major diamond deposit was discovered in Brazil. Brazilian diamonds dominated the market from the middle of the 18^th to the middle of the 19^th centuries. Now they can be seen only in antique jewellery. The history of modern diamonds began in 1866, when a 21.25 carat gemstone was found in South Africa. This diamond was named "Eureka".

One of the first successful prospectors in Africa was Cecil John Rhodes. In 1888, he established the De Beers United Mines Company. The company was named in honour of the De Beers brothers, on whose farm the first diamonds were found.

Since then, the range of diamond suppliers has expanded significantly. Major suppliers and producers in Africa are Botswana, South Africa, Angola, Congo, Namibia, Sierra Leone, Central African Republic, Guinea, Lesotho. In Asia they are Russia and China, in north and South Americas -- Brazil, Venezuela and Canada and, finally, the famous “Argyle” and “Merlin” mines in Australia.

The first diamond in history was cut in 1454 by the jeweller Louis de Bernell. He made it for Charles the Bold, Duke of Burgundy (1433-1477), who having seen this magnificent sparkling stone, decided to decorate his armour with similar gems. Appearing at social events in diamond jewellery was introduced by Agnès Sorel (1422-1450), a favourite of King Charles VII of France. The concept of diamond as a synonym for wealth and luxury came into use in Russia during the reign of Empress Catherine II. The diamond cut was created circa 1690 by the Venetian Vincenzo Peruzzi. In 1876, a new method of diamond processing was presented to the world in Philadelphia with the use of special equipment -- a stone-cutting machine. The method of grinding gemstones used by modern jewellers in their work has been in practice only since 1910.

The types of diamonds and their colour qualities and, consequently, their value, depend directly on the impurities they contain. Despite the small percentage of exogenic inclusions, they have a decisive influence on the colour and brilliance of the stones. Blue-coloured minerals are the result of boracium impurities, while pinkish minerals are the result of deformations that the crystalline grid of the stone underwent in the process of its complex formation. The unique property of a stone to emit light when exposed to X-rays depends on its nitrogen content. It is believed that the more nitrogen inclusions a mineral has, the brighter and more intense it will appear. The jewellery properties of diamonds are described using the 4 C's - cut, carat weight, colour and clarity. At the same time, 80% of all mined stones are unsuitable for jewellery and are used for the production of highly rigid cutting tools and special coatings.
Diamond is believed to be the king of stones, combining all possible mystical properties of minerals. It gives its owner health and strengthens memory (like emerald); protects from deception (like aquamarine); brings power over the minds and souls of people (like sapphire), etc. A diamond is also able to cure a person of fear and get rid of the evil eye.

The collection sections  "Decorative art and Jewellery”  and  "Clocks and Objects with Movement"  feature a variety of items decotated with diamonds. Here are some of them:

Tobacco box with singing bird, musical mechanism and clock. Jean-George Rémond, Switzerland, Geneva. Early 19^th century.

Snuffbox with timepiece insert in Louis XVI style. Piguet & Capt, Lechopié. Switzerland and France, Geneve, movement – Paris. Circa 1805
Boat shaped tray with dragon fly. Western Europe. Circa 1890
Musical snuffbox with singing bird, musical movement and clock. Jran-George Remond. Switzerland, Geneve. Early 19th century
Easter egg “Flower of Mexico” with the detachable brooch-flower. Wild, Manfred, Emile Becker firm. Germany, Idar-Oberstein
Tie pin. A. Tillander firm. Russian Empire, Saint Petersburg. Before 1908
Decoration for corsage "Dragonfly girl". Fyodor Lorie firm. Russian Empire, Moscow. 1899-1908

On the cover: Open face watch with matching chain and lapel brooch. Chaude. France, Paris. Сirca 1867

*The Mohs scale of mineral hardness (/moʊz/) is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material.