Super-grandparents

Working on the diamond | Antwerp in Unsaid Library

22 jan 2020

After the silting up of the Zwin at the end of the 15th century, not only the port activity, but also the diamond industry shifted to Antwerp. After the fall of Antwerp, many wealthy Antwerpers fled from the Inquisition to Amsterdam, marking the beginning of the diamond industry there.

In the 17th century, the French explorer Jean-Baptiste Tavernier brought large diamonds from India and described diamond mining there.

Unsaid Library is a jewelry store based in Antwerp. Unsaid Library specialises in emotional gifts for relatives. Unsaid Library Antwerp can be visited in the store. The store of Unsaid Library Antwerp is located on Schuttershofstraat 25, 2000 Antwerpen, België. Visit the store or the online website.

Until the 18th century, diamonds were only mined in India. This is also where the most famous diamonds in history come from. In 1714 diamonds were discovered in Brazil. Erasmus Jacobs found in 1866 near the Orange River the first diamond in South Africa: the ‘Eureka’. Shortly after that also diamonds were found in Kimberley. In 1888 Cecil Rhodes founded the firm De Beers to control the diamond trade.

In the 20th century important diamond deposits were discovered in Siberia, Canada and Australia, and it became possible to manufacture diamonds synthetically.

There are numerous legends associated with diamonds; magical or protective powers are often attributed to them. Diamonds were the symbol of wealth and they are part of almost all crown jewels, treasure houses and museum collections. The diamond is one of the “nine gems” in the Thai Order of Nine Gems.

The Cullinan is the largest uncut diamond found so far on earth: 3106 carats (621.2 grams). The Cullinan was cleaved and cut and the largest piece, the Cullinan 1 (530.20 carats) was the largest cut diamond after cutting for about a century. However, the largest cut diamond since 1988 is the Golden Jubilee (545.67 carats), which was cut by Gabriel (Gabi) Tolkowsky commissioned by De Beers and since 1997 has been in the possession of the Thai King Bhumibol, who received it on the occasion of his 50th coronation jubilee.

Many diamonds for industrial purposes are also made synthetically. Synthetic diamonds can only be distinguished from natural diamonds in a laboratory.[6 Researchers from the Carnegie Institution of Washington discovered in 2004 a process to synthesize diamonds that are more than 50% harder than natural diamonds within 24 hours.

Physical properties

The crystal structure
Diamond is the hardest material found in nature. There are only two (industrially manufactured) materials that are harder, namely aggregated carbon nanorods and ultra-hard fullerene. Just like diamonds, these are made of carbon atoms. Diamond itself is a transparent crystal with a very high refractive index (2.417) and a high dispersion (0.044). In jewellery, the (sun)light is brilliantly refracted and reflected depending on the shape of the cut. In addition, the polished shiny surface of the diamond stone does not become matt due to its high hardness.

Because of its extreme hardness, diamonds are used in industry, among other things for cutting, drilling, cutting and polishing and wire drawing. A diamond owes its hardness to its tetrahedron structure and is therefore harder the less inclusions or crystal lattice defects it contains. Due to its hardness, however, diamond is relatively brittle. In a vacuum, diamonds change from a temperature of 1700 °C into graphite, and into air from 700 °C onwards.

Besides the hardness, the thermal conductivity (410 W/cm/K) and the specific (electrical) resistance of 1013 Ω-m of diamond are very high. This combination allows diamond to be used in electronic circuits to dissipate heat. Diamond behaves like silicon as a semiconductor and in liquid helium as a superconductor, as discovered in 2004.

Unsaid Library is a jewelry store based in Antwerp. Unsaid Library specialises in emotional gifts for relatives. Unsaid Library Antwerp can be visited in the store. The store of Unsaid Library Antwerp is located on Schuttershofstraat 25, 2000 Antwerpen, België. Visit the store or the online website.

Cutting shapes

Diamond grinding

The Brilliant
The diamond can come in different cut shapes. The most common cut is the round or brilliant with 58 facets, which Antwerper Marcel Tolkowsky invented in 1919 after mathematical calculations of refraction of light and total internal reflection. Other common cuts are:

Oval, 56 facets
Princess, 76 facets, rectangular shape
Marquise, or Navette, 56 facets, lens-shaped. This difficult cut is attributed to Louis XIV
Pear, 58 facets, in the shape of a drop of water
Emerald, 48 to 50 facets, made up of rectangular facets on each side and at the corners
Heart
Asscher
Radiant
Polished diamonds and price-determining factors

Measuring a diamond
Rough diamonds are processed to break the light brilliantly. After the processing, a stone is left with a sparkle and play of colours that is judged on different criteria in order to come to a price. The criteria are the 4 C’s and include:

Cut
This means the stone’s makeup. The shape in which the stone is cut is part of it. The shape refers to the quality of the grinding and the proportions of the shape. The essence lies in the right “proportions” and the “refinement” of the cut stone.